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Owens Peak #7: Liverworts (Including Palomar College Arboretum)
This is a separate section devoted to these primitive nonvascular plants. They represent a glimpse into early land plants on Earth long before the age of dinosaurs. Many of the images are from the coastal sage scrub adjacent to the Palomar College Arboretum. This hillside area is separated from Owens Peak by a large parking lot and road. The coastal sage scrub habitats are essentially the same. Some of the same bryophytes and lichens occur in both areas, particularly along shady, roadside banks on the north side of Owens Peak. Like the cryptobiotic crust of desert areas, these minute plants are fragile and vulnerable to foot traffic, bicycles and motorized vehicles.

Most of the liverworts on this page were found on moist shady banks in coastal sage scrub on Owens Peak & nearby hills, and in the Palomar College Arboretum during January 2020.

Miniature forest of mosses (foreground) & liverworts in Palomar College Arboretum (January 2020).
In the life cycle of liverworts and mosses, the conspicuous, green plant is the haploid gametophyte generation. It produces the male (sperm-bearing) sex organs (antheridia) and female (egg-bearing) sex organs (archegonia). Species with separate male and female individuals in the population are referred to as dioecious. Species with both sex organs on the same individuals are monoecious. In the following oversimplified illustration I compared the life cycle of a moss & liverwort with a human. The diploid sporophyte generation is reduced to a spore-bearing sporangium and a few other structures depending on the species. During my 40 year career of teaching botany & biology to Palomar College students, I found that students generally related to the following life cycle:

Liverworts and mosses were once placed in the phylum (division) Bryophyta (bryophytes), embryo-producing plants (embryophytes) without a water conducting system (nonvascular). As a young student in a botany class at Arcadia High School, I was very fond of liverworts and there was a nice population of Marchantia on the shady, north side of our biology lab room. DNA research has resulted in a detailed evolutionary tree for the plant kingdom. The primitive nonvascular bryophytes represent three clades (branches) or offshoots from the base of the tree that are often treated as divisions: Marchantiophyta (liverworts), Bryophyta (mosses) and Anthocerotophyta (hornworts). Hornworts are especially interesting because they greatly resemble some of the earliest land plants on Earth. The Marchantiophyta include thalloid liverworts (class Marchantiopsida) with a plant body called a thallus. Leafy liverworts belong to class Jungermanniopsida.

Cladistic analyses suggest that the hornworts (Anthocerotophyta) originated much earlier in the history of land plants, possibly before the Devonian. Fossil bryophytes are scarce, but some bryophyte-like fossils have been found in Carboniferous deposits (300 million years ago) and older. Hornworts may even be one of the earliest lineages of land plants. Some of their morphological characteristics are similar to sporophytes of the ancient land plant Horneophyton that lacked true vascular tissue. In fact, some paleobotanists have suggested that Horneophyton may be the "missing link" between hornworts and the Rhyniopsida, an extinct class of early vascular plants. Fossils of these ancient land plants are well represented in the early Devonian Rhynie Chert beds in Aberdeenshire in the north of Scotland. This time period is approximately 398-416 million years ago, long before the age of dinosaurs. Hornworts are certainly one of the most unusual and fascinating plant groups on earth. On a road trip from Banning to Idyllwild I once stopped at a roadside seepage area and, lo and behold, I found a population of hornworts!

In case you are wondering how far back in time is the Devonian Period (400 million years ago), see the following geologic time scale that I created in html code. Hornworts are mentioned in red because they greatly resemble some of the earliest land plants, such as Horneophyton & Rhynia.

Era
Period
MYA
Cenozoic
Tertiary
5-6
10
25
50
64
Silver Sword Alliance: Ancient Tarweed Reaches Hawaiian Islands
Santa Rosa Basalt & The Endemic Santa Rosa Brodiaea
Dominican Republic Amber (Miocene)   W. Indian Locust & Copal
Baltic Amber (Shores Of The Baltic Sea)
Avian Dinosaurs Survived K-T Mass Extinction
Mesozoic
Cretaceous
65
70
71
90
95
100
135
140
K-T Boundary--Giant Asteroid Hit Earth: Mass Extinction Of Dinosaurs
Hell Creek Formation, Mont.: Ficus ceratops = Spinifructus antiquus
Sauropod Dinosaur Dung In India With Phytoliths!
Metasequoia Fossils Resembling Present-Day "Dawn Redwood"
Ancient Flowering Plants: Nymphaeales (Water Lilies) & Magnoliales
Ants  Oldest Ant Fossils (Evolved From Stinging Wasps 110-130 mya)
Araucariads & Southern Supercontinent Called Gondwanaland
Origin Of Flowering Plants: Darwin's "Abominable Mystery"
Mesozoic
Jurassic
145
160
180
Santiago Peak Metavolcanics: Owens Peak
Jet: Carbonized Remains Of Ancient "Araucariad" Forests
Gingko: Ancient Gymnosperm   Plants Of Jurassic Park
Mesozoic
Triassic
200
225
245
Pangea: A Giant Supercontinent   Continental Drift (Plate Tectonics)
Petrified Forest NP: Once At Latitude Of Cen. Amer.  Taxonomy Issue
Osmunda Fern Fossils Resembling Present-Day Species In Canada
Paleozoic
Permian
250
Cycads & Conifers Flourish
Paleozoic
Carboniferous:
Pennsylvanian
Mississippian
300
300-360: Dominant Ferns, Horsetails, Club Mosses (Lycopds), Scale
Trees (cf. Sigillaria), Primitive Gymnosperms, Early Cycads, etc. Time
Of Extensive Swamp Forests & Massive Coal Formation.
Paleozoic
Devonian
400
Rhynie Chert, Scotland: Horneophyton & Rhynia--Earliest Land Plants
(Primitive, Leafless, Spore-Bearing Plants). Very Similar In Appearance
To Present-Day Hornworts (Division Anthocerotophyta: Anthoceros)
Paleozoic
Silurian
430
First Known Land Plants
Paleozoic
Ordovician
450
Marine Algae Dominant
Paleozoic
Cambrian
500
Algae & Invertebrates In Seas: Trilobites Dominant

  Hornworts On The Road To Idyllwild!  

Thalloid Liverworts (Class Marchantiopsida)

Asterella (a thalloid liverwort) near the summit of Owens Peak north of Palomar College. Possibly A. palmeri with mature archegoniophores bearing spore-bearing capsules (sporophytes) on their undersides. The small liverwort Riccia is prevalent on moist, shady banks along trails on north side of Owens Peak. Botanist Beth Pearson also reported the thallose liverwort called frillwort (Fossombronia). The species F. longisecta is listed for Orange and San Diego Counties.

Bluish-green species of Riccia (a thalloid liverwort) in Palomar College Arboretum & on Owens Peak. See how Riccia survives desiccation in the following image from Palm Canyon, Anza-Borrego Desert. .

The slender, black threads with dichotomous branching are the rolled-up, desiccated thalli of a liverwort. The hydrated green thalli have unrolled into their characteristic dorsi-ventrally flattened structure. This is a species of liverwort in the genus Riccia photographed in Palm Canyon, Anza-Borrego Desert.

Leafy Liverworts (Class Jungermanniopsida)

Frillworts (Fossombronia) On Slope Northwest Of Owens Peak

Light green leafy liverworts called frillworts (Fossombronia) on wet, shady bank along trail northwest of Owens Peak (photographed 14 January 2020). Later in spring spherical black sporangia are produced. I have walked on these trails for more than 40 years, but never recognized this remarkable liverwort until Beth Pearson brought it to my attention! Special thanks to Beth. The bluish-green liverwort in photo is a species of Riccia.

Frillworts are small, delicate leafy liverwort species growing on moist soils throughout our planet, from subarctic to subantarctic and on all major continents. Under a dissecting microscope the leaves appear like clothing frill, defined as gathered, pleated, or bias-cut fabric edging used on dresses and blouses. Some types of lettuce also have leaves that appear frilled. The name frillwort: is derived from "Frill" + "Wort" (old English word for plant). The best way to describe the appearance of frillwort leaves is with the following image comparing clothing frill with frillwort plant in Palomar College Arboretum.

Frillworts (Fossombronia) In Palomar College Arboretum!

Doyle, William T., and Stotler, Raymond E. 2006. "Contributions Toward a Bryoflora of California III. Keys and Annotated Species Catalogue for Liverworts and Hornworts." Madroņo, 53 (2) : 89-197.

1. Spores typically with 11 to 28 lamellae around the circumference as seen in equatorial
optical section with the compound microscope; lamellae of spores spaced 4.5–10 mm apart,
in side view; leaf attachment usually does not exceed the midline on the dorsal stem surface
of vegetative plants................................................................................................. F. pusilla

1. Spores typically with 30 to 44 lamellae or spines around the circumference as seen in
equatorial optical section with the compound microscope; lamellae or spines of spores
spaced 1.5–3.5 mm apart, in side view; leaf attachment usually exceeds the midline on the
dorsal stem surface of vegetative plants............................................................ F. longiseta

Upper left: Clothing frill compared with frillwort (upper right). Lower Image: Frillworts compared with U.S. penny that is 19 mm in diameter. In this image they resemble a Lilliputian garden of ruffled leafy lettuce!

  Size Of U.S. Penny Used In Wayne's Word Images  
See Updated Design Of The Classic Lincoln Penny

Close-up view of frillwort showing frilled leaves.

Light green frillworts (Fossombronia) on moist ground along trail in Palomar College Edwin & Frances Hunter Arboretum. Another amazing discovery by botany professor Beth Pearson & 2 of her great students.

Microscopic view of frillwort in Palomar College Arboretum showing cellular structure of leaf (left) and immature (green) sporangium (right). The simple flattened leaves are only one cell-layer thick. The cells contain minute chloroplasts.

Microscopic view of frillwort spores taken from dark brown sporangium. The spores are 35 to 55 µm in diameter. The elongate, hygroscopic cells with helical bands of wall thickening are elaters. Their shape changes in response to changes in moisture. As the sporangium dries, the elaters facilitate dispersal of spores. Two species of frillworts are known for California, Fossombronia pusilla and F. longisecta. Their ID is based on spore structure. You can observe lamellae around circumference of spore in an equatorial optical section with compound microscope (substage illumination). Another interesting fact, bottleworts of the genus Sphaerocarpos do not have elaters. Magnification 1000x.

Using 100x oil immersion objective (1000x magnification) and focusing up & down due to limited depth of field, I can barely count the lamellae at circumference of spore. I cannot even come close to the number range (30-44) described by Doyle & Stotler (2006) for Fossombronia longisecta. F. pusilla has 11-28 lamellae (layers) and my count is at least a dozen lamellae. It is possible that my equipment (and microscope skills) are not up to par for this critical observation; however, I stand by my determination of F. pusilla for the Palomar College Arboretum. In addition, F. pusilla is listed for San Diego County by Doyle & Stotler (2006). Note: This image uprezzed with Photoshop plugin Genuine Fractals.

Close-up view of frillwort sporangia on minute transparent stalks. This is the diploid sporophyte generation of frillworts. The fertilized egg within archegonium on female plant develops into a diploid sporangium that is elevated by a stalk (seta) for more efficient spore dispersal. Hygroscopic elaters help to release the densely packed spores within the sporangium.

Mature spores and elaters from sporangium in previous image. The characteric lamellae are more pronounced in younger spores before stalk formation (see above images). Magnification 400x.

Fossombronia pusilla has an enormous geographic range. In addition to North America, this species also occurs in Europe, Asia, Africa, and Australia. Its spores undoubtedly become airborne and travel across oceans to different continents. This remarkable phenomenon also occurs in some lichens and other spore-producing organisms.

Horsetails (Equisetum hyemale), a primitive vascular plant (pteridophyte) with jointed stems and a terminal spore cone (strobilus). Because this genus dates back to the Carboniferous era (300 million years ago), it is sometimes called a "living fossil." They are also called "scouring rushes" because the silica-impregnated stems were used to clean pots and pans. The sporangia within the strobilus also contain hygroscopic elaters similar to some bryophytes.

Magnified view of Frillwort (Fossombronia) leaf taken with compound microscope and substage lighting. The leaf is composed of a single layer of cells, each with numerous, minute chloroplasts. Unlike thallose liverworts there are no air spaces or external pores. (See next image.)
Thallose liverworts cannot control their water loss (transpiration) through the pores. Without a water conducting system of cells (vascular tissue) and without pores (stomata) controlled by guard cells, they typically live in shady, moist areas where they can imbibe water, and where there is sufficient water for their swimming sperm to reach the egg. However, there is now evidence that minute arthropods (collembolans & mites) may passively facilitate the transfer of sperm in mosses. As I stated above, frillworts (Fossombronia) can survive in relatively dry areas during summer and fall by the production of underground tubers. Magnification 400x.

Moss Fertilization By Microscopic Springtails
  Thallose Liverwort In Creek Near Walker River  


Without Water-Conducting Cells, Nonvascular Plants Must Be Small Like Liverworts

Left: Vessels from Brodiaea terrestris ssp. kernensis, a rare flowering plant in the vernal pool field near Palomar College. The spirally-thickened secondary cell walls appear like coiled springs. This provides strength as well as flexibility to these strands of tubular, water-conducting cells that compose the xylem (vascular) tissue. Right: Two types of water-conducting cells: tracheid and vessel (vessel element). Technically a vessel is composed of many hollow vessel elements joined end-to-end like sections of PVC pipe. Vessels are characteristic of all flowering plants, except for the earliest ancestral sister clade (Amborella) that have only tracheids like most gymnosperms.
Without Guard Cells, Liverworts Cannot Control Water Loss
Through Their Pores. They Typically Live In Moist Places
Microscopic view of the paired guard cells and stoma on the leaf surface of a flowering plant (Tradescantia). An opening or stoma develops between the inflated (turgid) guard cells due to a differential thickening of their walls. When the guard cells lose water pressure on a hot day, they deflate and push together, thus closing off the stoma and reducing water loss (transpiration) through the leaf. During January 2020 liverworts were abundant in the Palomar College Arboretum in exposed areas with full sun. This is due to substantial rains in December 2019 producing moist soils conducive to spore germination. I might add that frillworts (Fossombronia) can survive in relatively dry areas during summer and fall by the production of underground tubers.


Bottleworts: Fascinating, Minute, Thalloid Liverworts

Botanist Beth Pearson & her student Isabelle also discovered bottleworts (Sphaerocarpos) in the Arboretum. Bottleworts are in the thalloid liverwort class Marchantiopsida with a plant body called a thallus. The erect bottle-like structures (involucres) with an opening at tip surround the female sex organs (archegonia) and the spore-bearing capsule (sporangium) after fertilization.

The following reference separates the four California species of Sphaerocarpos by their spores. Spores of S. drewiae remain united in tetrads after capsule dehiscence. The tetrads are lamellate with parallel ridges. S. michelii and S. texanus have areolate spore tetrads. Spores of S. cristatus are smaller and separate long before capsule maturity. I originally thought we had S. cristatus and S. texanus in the Arboretum; however, I now believe that my S. cristatus conclusion was premature and incorrect. The sporangia I examined in early February were immature (transparent, wet & slimy) and tetrads may not have formed yet. In fact, I may have been photographing spore mother cells (sporocytes) prior to meiosis. The sporangia I observed in late February contained distinct, dark brown or black tetrads under 400x magnification with a compound microscope.

According to Occam's razor (principle of parsimony), when there are several tentative explanations (hypotheses), the one that makes the fewest new assumptions is probably the best explanation. In other words, do not generate a hypothesis any more complex than is demanded by the data. In this case, since the sporangia I observed in early February 2020 were clearly immature, I cannot conclude that spores had already separated from tetrads following meiosis. I.e. spores could have been united in tetrads after capsule dehiscence.

As of 29 February I was not positive on my identification of Sphaerocarpos texanus. The spores were clearly released from sporangia in tetrads, but without an scanning electron microscope I just couldn't see detail of the spore surface. I finally examined a sample of dark spore tetrads with a compound microscope with a bright light above the stage. Low & behold there were parallel ridges on spore surface! This has to be the rare & endangered bottlewort Sphaerocarpos drewiae (also spelled S. drewei) endemic to California. It has a California Native Plant Society rating of 1B.1: Seriously endangered in California due primarily to habitat destruction. NatureServe Explorer rates this species as G1 Critically Imperiled. Their next higher rating is "Possibly Extinct." This discovery should be documented for the Palomar College Arboretum. It is possible that a second species of Sphaerocarpos occurs in the Arboretum area; however, I believe that the different initial names I came up with were premature conclusions based on images of different stages of spore development from the same species.

Sphaerocarpos drewiae is certainly not commonly observed. In addition to its critically endangered status it is a very small plant, especially the male plants. During my research on the population near Palomar College Arboretum their growth cycle was very short. Plants in January & February 2020 were bright green; however, by 14 March 2020 they were black and already decaying. In fact, they were difficult to distinguish from the dark, wet soil after recent rains. It is doubtful that a casual observer walking on this road could recognize these rare plants at this stage of their short life.

CNPS Rare Plant Inventory Status For Sphaerocarpos drewiae
  IUCN Redlist Of Threatened Species For Sphaerocarpos drewiae
  NatureServe Explorer: Sphaerocarpos drewiae Critically Imperiled  

  Images Of Decaying Bottleworts On This Page  

According to Stotler, R., & B. Crandall-Stotler (2017), Sphaerocarpos drewiae was named in 1929 to commemorate Miss K.M. Drew, in which case the epithet should end in "iae" not "ei" or "ii" in compliance with Article 60.12 of the ICN (Mcneill et al., 2012). For a "Mr. Drew," it would be drewii. Most references list this species as drewei. According to Pronunciation of Biological Latin by Peter Ommundsen (accessed 9 June 2020) the correct pronunciation for this commemorative name (eponym) would be DREW-ee-ee. If it commemorated a male (drewii) the pronunciation would be DREW-ee-eye. I was taught to pronounce all of the vowels by Dr. Carl Sharsmith in his alpine & subalpine botany courses at Tuolumne Meadows, Sequoia National Park. Another botany professor just told me to just pronounce scientific names with authority!

The author of this species was Grace Wigglesworth, a prestigious bryologist who was curator of Manchester Museum at the University of Manchester, England. Dr. Kathleen M. Drew was a renown phycologist in the botany department at University of Manchester. She was known for her research on the edible red alga Porphyra (nori), which led to a breakthrough for commercial cultivation. In 1928 she married Manchester academic Henry Wright-Baker, which resulted in her dismissal by the university which had a policy of not employing married women. Kathleen Drew-Baker's scientific legacy is revered in Japan, where she has been named "Mother of the Sea." Her work is celebrated each year on April 14. A monument to her was erected in 1963 at the Sumiyoshi Shrine in Uto, Kumamoto, Japan.

Doyle, William T., and Stotler, Raymond E. 2006. "Contributions Toward a Bryoflora of California III. Keys and Annotated Species Catalogue for Liverworts and Hornworts." Madroņo, 53 (2) : 89-197.

Stotler, Raymond E. and Crandall-Stotler, Barbara. 2017. "A Synopsis of the Liverwort Flora Of North America North of Mexico 1,2." Annals of the Missouri Botanical Garden, 102 (4): 574-709. Missouri Botanical Garden Press.

1. Spores separating long before capsule maturity ............................................. S. cristatus
1. Spores remaining united in tetrads after capsule dehiscence ......................................... 2.

2. Spores lamellate with low, thick, nearly parallel ridges (a few areolae occasionally occur in
the middle of the outer face of each spore) ........................................................... S. drewiae
2. Spores areolate, never with parallel ridges ...................................................................... 3.

3. Areolae with prominent protuberances at the corners of the areolae (view in
silhouette) .............................................................................................................. S. michelii
3. Areolae of spores lacking prominent protuberances at the corners of the areolae (view in
silhouette) .............................................................................................................. S. texanus

The following articles are from Royal Botanic Garden Edinburgh showing SEM images of the spores of S. drewiae taken by botanist Dr. Daniela Schill. Dr. Schill is also working on the phylogeny of Sphaerocarpos, including a DNA cladogram of all species in the genus.

Different genes within the nucleus and cytoplasmic organelles (chloroplast and mitochondria) can be used to construct phylogenetic trees called cladograms. One gene in the nucleolus codes for the smaller subunit of the ribosome. The gene is called SSU rDNA or small subunit ribosomal DNA. Base sequences from this gene are sometimes used to compare taxa at the species level. Chloroplast DNA, including the protein-coding rbcL gene, is often used at the family level to show the relationships between genera and species within the family. In DNA comparisons between species, stable, non-coding spacer genes are also used. DNA phylogeny can be difficult and problematic in some genera, including oaks (Quercus) and bottleworts (Sphaerocarpos). See the following article "Phylogeny of Sphaerocarpos (Difficulty in Gene Sequencing)" by Daniela Schill:

2 Articles Posted By Dr. Laura Forrest In 2016, RBGE
Preview to a Monograph: Sphaerocarpos drewiae Spores
  Phylogeny of Sphaerocarpos (Difficulty in Gene Sequencing)  

Brief Synopsis Of Sphaerocarpos drewiae Discovery In The
Palomar College Arboretum & Adjacent Coastal Sage Scrub

During January - February 2020 I attempted to identify a minute liverwort on trails in the Palomar College Arboretum and adjacent coastal sage scrub. Although I have annotated native flowering plants & primitive vascular plants (pteridophytes) in this region of San Marcos during the past 40 years, including rare & endangered species, I overlooked this minute nonvascular plant. For identification I used the excellent key in Doyle, William T., and Stotler, Raymond E. 2006. "CONTRIBUTIONS TOWARD A BRYOFLORA OF CALIFORNIA III. KEYS AND ANNOTATED SPECIES CATALOGUE FOR LIVERWORTS AND HORNWORTS." Madroņo, 53(2): 89-197. Initially I thought it might be S. cristatus with single spores not in tetrads; however, I now believe the sporangia were too immature for valid spore identification. On 16 February 2020 I found mature spores in tetrads so S. cristatus was excluded. Then I thought it might be S. texanus because it had spores in tetrads and is the most commonly seen species in California. It is even on the Montenegro postage stamp; however, I never felt 100 percent certain because I could not see the detail of tetrad surface with my equipment and I did not have access to a scanning electron microscope (SEM). The spores are too small for a dissecting microscope or close-up camera lenses with extension rings. On 29 February 2020 I tried a compound microscope with substage lighting and a bright dissecting microscope illuminator from above (without cover slip). Lo and behold, at 400x magnification the spore tetrads revealed parallel ridges! My image isn’t as good as a SEM but it is sufficient to identify this bottlewort as S. drewiae, the rare & endangered California endemic species! Its rating by CNPS is1B.1, a rare, seriously endangered little plant indeed. Its state & global ranking is S1 & G1: Critically imperiled. As usual, its threatened status on our planet is primarily due to habitat destruction where land developers bulldoze our environment for more housing & urbanization. This needs to be documented for the Palomar Arboretum & adjacent coastal sage scrub. Hopefully, its location on Palomar property will insure its survival amidst a sea of urban sprawl in coastal San Diego County.

Bottlewort Revelation #1: Spores United In Tetrads (24 Feb 2020)

I finally collected plants with mature spores released from sporangium and they are clearly in tetrads and without spines (prominent protuberances). This excludes Sphaerocarpos cristatus. I originally thought this might be S. texanus, the most commonly collected species in California and the species on Montenegro stamp! The pattern on spore surface is important for identification and difficult to see without a scanning electron microscope. See Bottlewort Revelation #2:

Note: Although I have placed approximate magnifications in my captions, this is a useless number, especially when images have been zoomed in with my Sony W-300 camera and cropped in Photoshop. In the case of Sphaerocarpos drewiae, the largest spore tetrads I examined were about 115 micrometers in diameter. I calculated this number using a compound microscope with 100x objective (1000x magnification) and field of view of 0.178 mm (see image below). Most references give numbers of 125 - 163 micrometers in diameter.To appreciate their small size, the length of a one-celled Paramecium bursaria or a Demodex mite from a pore on the author's nose is about 180 micrometers (0.180 mm). Sphaerocarpos drewiae spore tetrads are roughly comparable in size to the smallest orchid seeds. These objects are barely at the resolving power of an unaided human eye with 20-20 vision. See link to Wayne's Word Table Of Cell Sizes after following image.

Bottlewort Spores Are Really Small!
Here are spores of Sphaerocarpos drewiae compared with a grain of table salt from my kitchen salt shaker. Note parallel ridges on spore surface that are characteristic of this rarely observed species.

  Wayne's Word Relative Sizes Of Cell & Viruses   

Bottlewort Revelation #2: Parallel Ridges On Spore Surface (29 Feb 2020)

With substage and above-stage lighting the parallel ridges on surface of spore tetrads are visible. This keys out to the native California bottlewort Sphaerocarpos drewiae. When I saw the parallel ridges I could barely contain my excitment! Magnification: 400x

Image taken with compound microscope and substage lighting. I also used a dissecting microscope illuminator for above lighting to show parallel ridges on tetrad surface. The best results were obtained from dry spore tetrads without a cover slip. I used 10x objective for maximum depth of field; however total magnification in this zoomed in, cropped image is about 350x

For those who might question my ID of the rare Sphaerocarpos drewiae (S. drewiae) in the Palomar College Arboretum & adjacent coastal sage scrub please look at the following image comparison. I took the liberty of posting the SEM image by Dr. Daniela Schill (Royal Botanic Garden Edinburgh) side-by-side with my compound microscope image. According to the references of have consulted, this is the only species in California with parallel ridges on surface of spore tetrad as shown in both images.

Images Of Bottleworts In The Palomar College Arboretum

Several bottlewort plants (appearing like tiny green clumps) in the coastal sage scrub above Palomar College Arboretum. See next image to see how small these plants are. I never saw one in all the 40+ years of hiking in these hill until botanist Beth Pearson showed me then on 23 January 2020!

The bottlewort clumps are less than 10 mm across. The U.S. penny is 19 mm in diameter. You really need to get down on your knees to observe these plants.

An ordinary straight pin is used for a size relationship. The upright bottle-shaped structures are involucres containing female sex organs called archegonia. In fact, bottleworts are dioecious with separate male and female plants.

Close-up view of bottlewort taken with Nikon SLR and extension rings. This is a thalloid liverwort, unlike the leafy frillwort. Each bottle-shaped involucre has an opening at its top.
Note: In March-April, a spherical (globose) sporangium develops inside each involucre. The spores escape through opening at the top or when the involucres break apart. THERE IS NO UPRIGHT STALK WITH A GLOBOSE OR UMBRELLA-LIKE SPOROPHTYE. Literally thousands of spores are released among the old involucres, some of which go into the air on a windy day.
The bottlewort (Sphaerocarpos texanus) appears on a stamp in the country of Montenegro in southern-southeastern Europe. Montenegro is a Balkan country with rugged mountains, medieval villages and a narrow strip of beaches along its Adriatic coastline. Sphaerocarpos texanus has a worldwide distribution. In fact, it also occurs in California, including San Diego County.

Close-up view of bottlewort involucre & illustration of minute plant.

Tiny bottlewort like in above illustration sitting on U.S. penny.

  More Images Of Terrestrial & Aquatic Liverworts  
Origin Of The First Land Plants On Planet Earth

Another Bottlewort Population Along Upper Trail Southeast Of Arboretum
Through Coastal Sage Scrub. The Bottleworts Extend Out Into The Trail!

Bottleworts are dioecious, a term referring to a species population containing male and female individuals. It is not the same as bisexual! Male plants are exceedingly difficult to spot because they are very small and often crowded between clusters of female plants. Like female plants, their involucres sit upright on the surface of a minute thallus. They are often reddish purple, especially when growing in sunlight.

Bottleworts In March At The End Of Their Growing Season
Involucres & Thallus Are Decomposing But Black Sporangia Are Visible

It is very difficult to spot desiccated botteworts on dry ground. In fact, they are so difficult (if not impossible) to spot during most months of the year, I decided to give 2 GPS locations of Sphaerocarpos drewiae (S. drewiae) for bryologists interested in my page.

  33.149676 N, 117.179368 E;   33.149708 N, 117.179502 E  

Minute bottlewort sporangia among decaying, black plants. They are spherical (globose) structures resembling microscopic black BBs.

Bottleworts on upper road in Palomar College Arboretum (14 March 2020). Most of the plants are black and barely recognizable on the wet soil following a heavy rain. A spherical bottlewort sporangium is circled in red. Several minute, black sporangia are visible among the decaying plants. They each contain at least 50 or more spore tetrads. This scenario is exactly what happened to the plants I attempted to grow at my home. In the above image there are several small plants that still have green involucres. Most of the bright green plants of February turned black within the first two weeks of March. It is doubtful that a casual observer walking on this road could recognize these rare plants at this stage of their short life. The U.S. penny is 19 mm in diameter.

Close-up view of bottlewort sporangia compared with ordinary straight pin.


Desert Cryptobiotic Crust

Bryophytes and lichens are important components of desert cryptobiotic soil crust and we have some of these in the Palomar College Arboretum and adjacent coastal sage scrub. In fact, one is a white soil lichen near the bottlewort population on upper Arboretum trail. See following reference:

A Field Guide To Biological Soil Crusts Of Western U.S. Drylands: Common Lichens & Bryophytes
by Roger Rosentreter, Matthew Bowker, & Jayne Belnap. 2007. U.S. Geological Survey

  Field Guide To Cryptobiotic Soil Crusts In The Western United States  

This is a thin whitish lichen crust with granular (powdery) soredia and few fungal apothecia. It appears after winter rains and often disappears during the dry weather of late spring and summer. It may be in the genus Trapeliopsis, possibly T. granulosa.

Microscopic view of soredia from the granular (powdery) surface of Trapeliopsis, possibly T. granulosa. Each soredium contains several green algal cells enveloped by filamentous fungal hyphae. Like dust particles, the soredia are carried by the wind to different locations where they develop into new lichens. The upper surface of lichen thallus is covered with these minute soredia. This is how many lichen species spread to new locations. Why start from a fungal spore from an apothecium when you already have both symbionts in soredium: the photobiont (alga) and mycobiont (fungus). A fungal spore must land on suitable substrate and hopefully encounter its algal mate. Lichens are truly a "marriage" between algae and fungi.

I once worked with a student at Cal State University San Marcos who grew the algal & fungal components of the lichen "British soldiers" separately (see following link). British soldiers (Cladonia cristatella), is an attractive soil lichen with upright podetia bearing bright red apothecia at the tips. The fungus appeared like an amorphous blob of tissue while the algae appeared as bright green cells. Only in the combined lichen state does the true body form appear. This is an excellent example of synergism where the whole is truly greater than the sum of its parts. Using gel electrophoresis, the lichen DNA clearly showed gene activity not present in the symbionts.

  Symbiogenesis: British Soldiers  
Arid desert regions throughout the world where vegetation is sparse sometimes develop specialized communities of cyanobacteria, mosses, liverworts, and lichens. The surface soil is held together by these associations called "cryptobiotic soil crusts." These crusts are very fragile and are easily damaged by walking on them. After sufficient rains, some of the small nonvascular plants and lichens turn greenish. Even when dry they form a protective crust layer. Cryptobiotic crusts are very beneficial because they hold soils in place and protect the underlying sediments from erosion. They are also an important pioneer stage in succession on bare ground (xerarch succession), thus enabling grasses and herbs to become established. In fact, the above lichen (Trapeliopsis) has been dissiminated in recently burned forests of Quebec.

Another White Crustose Soil Lichen In The Arboretum & On Owens Peak

  Cryptobiotic Crust In Anza-Borrego Desert  


Primitive Vascular Worts In The San Marcos Area!

I probably should mention two more interesting, primitive vascular worts (pteridophytes) in a vernal pool field near the William R. Bradley Park: Pillworts (Pillularia) and quillworts (Isoetes). When I majored in botany at California State University, Los Angeles I only saw these plants preserved in jars or pressed and dried on herbarium sheets. Unfortunately, the field is for sale and the vernal pools, several federally endangered plants and the San Diego fairy shrimp are threatened due to land developers in this pro-growth area. Some of these plants also occur in a nearby, small, fenced, mitigation preserve adjacent to Fry's Electronics.

  
Quillworts, Spike-Moss & Pillworts: Primitive Pteridophytes, Some With Tree-Like
Ancestors That Flourished During The Carboniferous Time 300 Million Years Ago
  
  Vernal Pool Field Near Palomar College  
Pillworts & Quillworts Near Fry's
Beautiful Rare Brodiaeas

Spike-moss (Selaginella) is an interesting pteridophyte that grows on boulders in the hills east of campus. Although often mistaken for a moss, this is a non-flowering, vascular plant that produces male and female sporangia in the leaf axils. There are 2 species on Owens Peak, S. bigelovii and S. cinerascens. Although horned lizards once roamed Owens Peak, I haven't seen one in years. They were often collected by people who tried to feed them lettuce and other greens. Their diet is 100 percent ants--mostly large black carpenter ants (Messor andrei) which are also rare on the peak (at least as of Jan. 2020).


Ancient Cone-bearing Trees & Cycads

Any discussion of ancient plants would not be complete without mentioning cycads and cone-bearing trees with ancestors that lived during the dinosaur era. We have some excellent examples of this Jurassic flora on the Palomar College campus and Arboretum.

  Cone-Bearing Trees & Cycads In Palomar Arboretum  
Plants Of Jurassic Park: Living With Dinosaurs
Distribution Of Cycads & Continental Drift
Living Fossils At Palomar College