Key to species Overview of the genus Morphology
When first learning to identify Frullania species it helps to have adequate material and especially material bearing perianths. Perianths are generally recognizable in the field with the aid of a hand lens. When documenting total diversity, collect sizable swaths of bark supporting Frullania with the aid of a 1-inch wood chisel. You will find the chisel superior to any knife. With a chisel it is easy to shave off a piece of bark by hand (no hammer needed) or remove ridges of bark. In the driest circumstances Frullania patches may be restricted to tree boles at ground level or restricted to the narrow confines of bark crevices. The wood chisel is an apt tool for cutting bark from the sides of deep crevices. On smooth barked trees such as American beech and young red maples, you may find that whole mats of intact Frullania can be dislodged from the bark without leaving any scar on the tree. In fact, in most cases it is not necessary to cut so deeply as to expose the tree’s xylem when removing intact bark substrate. Scars left from cutting into the inner bark are less damaging and less noticeable than scars that reach xylem. As in other bryophyte collecting, paper bags or paper packets are used to temporally store collected material.
Frullania specimens often consist of less than exemplary material. As early successional plants on young tree trunks, there appears to be an aging phenomenon whereby once vigorous patches begin the slow process of death and decay. Reduction of vigor with age may be brought about by an increase in shade due to changing forest conditions. Even as vegetative shoot sectors begin to decompose or are marred by excessive coverage of cyanophytes and other microbes, abundant fertile perianths may still be found; however, clear observations of vegetative characters will be blocked by decomposition of shoots. In healthy material placed in a wet mount, rhizoids arising from the base of underleaves may retain pieces of bark, debris, and leaf fragments from neighboring shoots. These adherent fragments block all transmission of light making the detection of underleaves and lobules difficult and should be removed by fine dissection if possible. Often only the last few pairs of leaves at the growing shoot tip offer useful characters. It is best to collect ample material to ensure the possession of demonstrable characters.
Begin by examining the intact community of liverworts with a dissecting microscope. This can be done initially with dry material to get a sense of the habit when dry; however, the most revealing views of morphology require examining fully hydrated communities. The following procedure is recommended.
For ease in scanning multiple bark chips, a rigid plate of some sort (rectangular acrylic sheet or lid to a large Petri dish) supporting the bark chips can be pushed back and forth by hand. A "push and pull plate" thus acts as a mechanical stage providing excellent control and precise positioning.
The above technique is also excellent to observe liverwort capsule dehiscence. When the specimen is removed from contact with the moist paper towel the dry atmosphere under the dissecting microscope often triggers mature capsules to dehisce. Dehiscence begins with the capsule valves separating rather rapidly, stretching the spring-like elators. The ends of the stretched elators are attached to the floor of the capsule and to the distal end of the inner capsule valves. Within a second or so the elators break contact with the floor of the capsule and spring upward instantly flinging the spores aloft. See the video below of F. inflata taken by Jessica Lenz during a liverwort lab for BI 362 Nonvascular Plants at the University of North Alabama.