Checklist of the Bryophytes of the Palos Verdes Peninsula – Neil Uelman (2024)

The PVP is home to many bryophyte species. These bryophytes can be found growing on soil, bark, rock, and other various substrates. Bryophytes are a group of land plants (embryophytes) that are comprised of three groups of non-vascular plants:

1. Mosses (Bryophyta)

2. Liverworts (Marchantiophyta)

3. Hornworts (Anthocerotophyta)

Click to access bryophyte-phylogeny-poster.pdf

Below is how to tell apart mosses, liverworts, and hornworts:

Liverworts and hornworts

• adult gametophytes leafy or thalloid, when leafy, usually bilaterally symmetrical
• leaves, when present, without a midrib (=costa)
• oil-bodies usually present in liverworts and absent in hornworts
• leaves of many species lobed
• rhizoids unicellular
• sporophytes either lack a meristem (liverworts) or have one between the foot and capsule (hornwort)

Mosses

• adult gametophytes leafy and mostly radially symmetrical
• leaves of most species with a distinct midrib (=costa)
• oil-bodies always absent
• leaves not lobed
• rhizoids uniseriate filaments
• sporophytes with an apical meristem

Bryophytes are small land plants that are found worldwide. They can be found in such places as the cold Arctic, hot, dry deserts, and wet lush rainforests. Bryophytes occur at sea level all the way up to alpine. All bryophytes reproduce sexually via spores rather than flowers or seeds, and their life cycle is dominated by the multicellular gametophyte (n) stage. The sporophyte (2n) stage for bryophytes is short-lived, attached to the gametophyte, and solely dependent upon the gametophyte for growth and survival. Bryophytes also need moisture to reproduce. Sperm is produced in antheridia. The sperm is released from the antheridia and swims through a thin film of water to the archegonia. The archegonia contain the ova and, once fertilized, produce the sporophyte.

Spore from a hornwort

Gametophyte (n) and sporophyte (2n) stages in a moss

Sporophyte of a moss (Amblystegium serpens) releasing spore. With changes in humidity, the peristome teeth flex in and then out to disperse the spore. 

The sporophytes of bryophytes are unbranched. Bryophytes can also reproduce asexually via fragmentation, gemmae, or other specialized structures.

Rhizoidal tuber – asexual reproduction

Leaf bulbils – asexual reproduction

Disc-shaped gemmae of Lunularia cruciata (liverwort)

All bryophytes lack true vascular tissue containing lignin; however, some bryophytes do have specialized water transport tissues. All bryophytes are poikilohydric, so they cannot maintain and/or regulate internal water content. In other words, if water is available, bryophytes are active and growing; however, if water is absent, then bryophytes become inactive and stop growing.

Videos of mosses rehydrating (mosses in the video have been dry for over a year). Once a drop of water is placed on the mosses in the videos, they immediately begin to rehydrate and become active:

Bryophytes do not have roots but rather structures known as rhizoids. These rhizoids are very fine (unicellular or multicellular) and extend from the lower epidermal cells. Rhizoids anchor bryophytes to whatever substrate that they are growing on. The rhizoids can help uptake water and minerals (mainly by capillary action) like vascular roots; however, rhizoids are not vascular in cell structure. Some species of bryophytes can take up water inside their rhizoids, but for most bryophytes, rhizoids are mainly used to anchor them to the substrate.

Rhizoids on a liverwort

Rhizoids on a moss

On the PVP, bryophytes can be found on soil, bark, rock, brick, and concrete. The most common substrate to find bryophytes on is soil. The PVP has both ephemeral species as well as perennial species of bryophytes. Hornworts and liverworts are uncommon and restricted to mesic areas on the PVP. Mosses are the most common and can be found in mesic areas as well as exposed sites on the PVP. Acrocarpous mosses and pleurocarpous mosses are found on the PVP.

Mosses growing on soil on the PVP

Mosses growing on bark on the PVP

Liverwort growing on soil on the PVP

Moss growing on a branch on the PVP

Moss growing on a rock on the PVP

Moss growing on brick on the PVP

So far, 75 species of bryophytes have been found on the PVP. The three most common bryophyte families encountered are Bryaceae, Pottiaceae, and Brachytheciaceae. Here is an unpublished species list for the bryophytes on the PVP.

Link to the Bryophyte chapter of California Native Plant Society (CNPS): http://bryophyte.cnps.org/index.php