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The Remarkable Liverworts: Especially The
Rare Bottlewort (Sphaerocarpos drewiae)
© W.P. Armstrong 1 March 2024   

My fascination with liverworts dates back to general botany courses at Arcadia High School & Mt. San Antonio College in the late 1950s & 1960s. I had 2 phenomenal teachers who also worked at the L.A. County Arboretum in Arcadia, my home town. Pictorial references about the life cycle of liverworts commonly discuss the genus Marchantia with distinct male & female gametophytes. In fact, they grew on the shady north side of a building at Arcadia High School! Haploid male & female plants bear erect, umbrella-like antheridiophores with sperm-bearing antheridia, and archegoniophores with egg-bearing archegonia. The diploid sporophyte is produced after fertilization on the female plant. There is very little pictorial information on the Internet about the gametophyte and sporophyte generations of seldom-seen bottle liverworts. In addition to the amazing historical significance of liverworts, with ancestral lineage dating back to the 1st land plants, this page includes images of both generations of the rare bottlewort (Sphaerocarpos drewiae) discovered in the coastal sage scrub near Palomar College.

Index Of Major Topics On This Page
1. The Remarkable Liverworts: Primitive Nonvascular Plants
Sections 2 - 6 refer to Bottle Liverwort (Sphaerocarpos drewiae)
2. Haploid Gametophyte: Green Plants Seen In Early Spring
3. Minute Haploid Spores That Grow Into Gametophyte Plants
4. Male Bottlewort Plant With Red Sperm-Bearing Involucres
5. Development of Diploid Sporangium Inside Female Involucre
6. Bottleworts at the End of Their Growing Season in Late Spring

1. Introduction: The Remarkable Liverworts: Primitive Nonvascular Plants

A generalized liverwort life cycle based on the genus Marchantia. The haploid male & female gametophytes bearing erect archegoniophore & antheridiophore are quite distinctive. The diploid sporophyte is essentially reduced to a spore-bearing sporangium. The green bottlewort gametophyte is minute, but visible to the naked eye, especially if you are on your knees; however, a magnifying glass really helps. The dark sporophyte (sporangia), after gametophyte has shiveled and turned black, is difficult to spot without magnification.
Public Domain Liverwort Illustration From Wikipedia Commons:
Fossil evidence of land plants (embryophytes) is scarce prior to the Silurian Period, although liverwort cryptospores have been found in Argentina dating back to early Ordovician about 470 milion years ago (C.V. Rubinstein, et al. 2010). The spore walls contained sporopollenin, one of the most stable biological polymers known and a characteristic of well-preserved pollen grains throughout the plant kingdom. The earliest land plants were probably similar to liverworts or hornworts with a dominant thalloid gametophyte generation and a reduced sporophyte.
Rubinstein, C.V., Gerrienne, P., De La Puente, G.S., Astini, R.A., and P. Steemans. 2010. "Early Middle Ordovician Evidence For Land Plants In Argentina (Eastern Gondwana)." New Phytologist 188 (2): 365-369
In case you are wondering how far back in time is the Ordovician Period (470 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. Rhynia also has characteristics similar to Psilotum.

Holocene Epoch: 1 January 2023: Day 8036 of 3rd Millennium AD
Wayne's Word Website Moved From Palomar College To Network Solutions
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
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"
Santiago Peak Metavolcanics: Owens Peak
Jet: Carbonized Remains Of Ancient "Araucariad" Forests
Gingko: Ancient Gymnosperm   Plants Of Jurassic Park
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
Cycads & Conifers Flourish
300-360: Dominant Ferns, Horsetails, Club Mosses (Lycopds), Scale
Trees (cf. Sigillaria), Primitive Gymnosperms, Early Cycads, etc. Time
Of Extensivive Swamp Forests & Massive Coal Formation.
Rhynie Chert, Scotland: Horneophyton & Rhynia--Earliest Land Plants
(Primitive, Leafless, Spore-Bearing Plants). Very Similar In Appearance
To Present-Day Hornworts (Division Anthocerotophyta: Anthoceros)
Marine Algae Dominant; First Known Land Plants
Liverworts Spores of Ancient Liverworts In Argentina. They evolved
from charophycean green algae. See Genus Chara in Ash Meadows.
Algae & Invertebrates In Seas: Trilobites Dominant
Archeocyathida: Ancient, Extinct Reef Builders
Ediacaran Biota in Shallow Seas: Precursors Of Lichens?
Cyanobacteria (Formerly Called Blue-Green Algae) Stromatolites

Left: A male Ash Meadows pupfish (Cyprinodon nevadensis ssp. mionectes). The submersed colonies of freshwater green algae are stoneworts of the genus Chara (phylum Charophyta). The numerous orange dots on the algae are sperm-bearing sex organs called antheridia (see following two images).

Right: Close-up view of the fruiting branches of Chara showing the easily recognizable sex organs. Although microscopic, the sex organs can be readily identified by their shape and color. The sperm-bearing antheridia are bright orange, while the egg-bearing oogonium is green with a distinctive crown of cells. This is an excellent alga for studying life cycles in general biology and botany classes.

1st Two Plant Phyla (Divisions) With Ancient Ancestry
Terestrial & Aquatic Liverworts (Phylum Marchantiophyta)
Hornworts (Phylum Anthocerotophyta): Also Ancient Lineage
Xerophyic Desert Liverwort: Thallus Rolls Up During A Drought
Frillworts (Fossombronia) On Hills Near Palomar College Campus
  Targionia: Widespread Liverwort On A Road Cut in Twin Oaks Valley   

Stages Of The Bottlewort Life Cycle

  Detailed Bottlewort Web Page At Network Solutions  
Formerly Residing On The Palomar College Server

2. Haploid Gametophyte: Typical Green Plant in Early Spring

This minute bottle liverwort grows in the coastal sage scrub at Palomar College. It is listed as 1B.1: "Threatened or Endangered" on CNPS Rare Plant Inventory (Code 1A is "Presumed Extirpated"). NatureServe Explorer lists it as G1: "Critically Imperiled." Its endangered status is primarily due to habitat destruction, a common occurrence in coastal southern California.

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.

3. Distinctive Minute Haploid Spores

The involucres and thallus are the haploid plant (gametophyte generation). It develops from a distinct, haploid spore characteristic of the bottlewort species Sphaerocarpos drewiae.

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.

For those who might question my ID of the rare Sphaerocarpos 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.

To Produce Spores, Female Plant Must Be Fertilized By Male Plant

4. Male Bottlewort Plant With Red Sperm-Bearing Involucres

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. Motile sperm are released from antheridium inside each involucre. They swim to nearby involucre of female plant when ground is wet. Fertilization occurs inside egg-bearing archegonium within involucre of female plant. The resulting zygote develops into a multicellular embryo and eventually into a sporangium. As the sporanium matures into a spherical spore-bearing structure, the female plant darkens and withers. By late spring, the dry ground has small black sporangia where the green bottleworts once grew.

5. Development of Diploid Sporangium (Sporophyte) Inside Female Involucre

6. Bottleworts At The End Of Their Growing Season
Length Of Growing Season Depends On Timing & Duration Of Rains
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. Depending on the timing & duration of winter & spring rains, bottlewort sporangia may appear in April or May.

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. A single sporangium is about 0.5 mm in diameter, slightly larger than an average grain of table salt (NaCl).