Friday, November 22, 2002
Name: Bazzania trilobata, a liverwort.
When and where seen: I saw some clumps this week in the Towle Woods near the edge of a dried-out vernal pond. I also saw some in the same area in March of this year, when the pond was full. It likes to grow in damp, shady places and can be seen all year round.
Distinguishing characteristics: Bazzania trilobata grows in mounds, often mixed in with moss. When dry it is bright green and when wet it is very dark green. The mound is made up of Y-shaped branching stems about two to four inches long. The leaves are arranged in two rows at right angles to the stem and overlapping like shingles. With a magnifying lens you can see the three teeth or lobes at the end of each leaf that give rise to the species name "trilobata". Towards the end of the lower fork on the right hand side of the photo you may be able to see the three lobes on one of the leaves. The entire piece in the photograph is about one inch long. On the underside of the stem is a single row of tiny leaves that hug the stem, and every quarter to half inch is a fine root-like thread that anchors the plant to its substrate.
The world of liverworts: Liverworts are spore-bearing plants and are sometimes collectively referred to as hepatics. There are two major groups: those with tiny leaf-like scales and those that are ribbon-like. Bazzania trilobata is an example of a leafy liverwort or a scale moss (not a true moss). The liverworts that you are most likely to see are the ribbon-like ones that grow flat on the surface of the soil around potted plants. The vegetative body of a liverwort has a distinct upper and lower surface, and a flattened appearance, which is a good way to distinguish them from mosses. Liverworts, as you may guess from their unattractive name, are among the lowlife of the plant kingdom. They have no xylem or phloem and therefore no true leaves, stems or roots. The "stem" is more properly called an axis; the "leaf" is a scale or a thallus, and the "root" is a rhizoid. Maybe English immersion will help with this.
References: Nina L. Marshall, Mosses and Lichens; Elizabeth Marie Dunham, How to Know the Mosses.
Submissions for the Biodiversity Corner are encouraged from everyone. The organism doesn't have to be elegant. The low-life slime balls and liverworts get equal consideration with lofty trees and soaring raptors. The only requirements are that it exists in the wild and was seen in Carlisle. Send a note to Kay Fairweather at 392 School Street, Carlisle MA 01741 or to firstname.lastname@example.org.
© 2002 The Carlisle Mosquito