COLLECTING AND PRESERVING MATERIAL. 405 



may be recognized by flattish green body about 1 cm. wide and 

 5-8 cm. long, attached by silky hairs. At some times it bears on 

 the upper surface sessile cups containing green grains, and sends 

 up erect slender sexual branches which spread out into flat heads 

 6-8 mm. across, some scalloped at edge and some with finger-like 

 rays. When cups or sexual branches are present no other liver- 

 wort can be mistaken for it. A very similar one, except in these 

 parts {Conocephalus conicus) may be distinguished by its larger 

 size and larger stomata, looking like needle pricks over the sur- 

 face, while those of Marchantia are just visible. It may be used 

 for the vegetative parts. Collect in July. Free from dirt as 

 much as possible, and preserve in formalin or 70$ alcohol. 



Porella. — Abundant everywhere on the bases of trees especially 

 in low grounds or wet bottom lands. It may be recognized by 

 its dirty-green pinnately branched shoots, 1-2 mm. wide, with 

 crowded overlapping rounded leaves. The plants are always in- 

 tricately interwoven. Flakes of the bark may be peeled off with 

 a broad knife or chisel, taking care not to tear up the plants into 

 too small patches. Collect in summer. Preserve dry, after dry- 

 ing under light pressure. Some should be kept in formalin or 

 alcohol for demonstration of finer structure of sex organs. 



Mnium. — Any species of the genus will do. The commonest 

 species eastward is M. cuspidatum. It is abundant everywhere in 

 patches on shady banks and in open woods about the bases of 

 trees. It may be recognized by the yellow or orange oval cap- 

 sule, thin and irregularly wrinkled when dry, horizontal or pen- 

 dent on a stalk 2-3 cm. long. The leaves are broadly oval, with 

 fine sharp teeth under lens, and a distinct midrib. When moist 

 the leaves are rather pale green, and not crowded or overlapping. 

 When dry the clump is a dull, dirty green, and the leaves are 

 much curled and twisted, expanding quickly when wetted. The 

 male and female organs are in the same cluster, at the apex of 

 the axis. Under the microscope the species may be recognized 

 by the orange inner peristome with double rows of perforations 

 in the membrane below the segments. Preserve as directed for 

 Porella. Almost any similar moss will serve equally well, espe- 

 cially the common species of Bryum. 



Equisetum. — The gametophytes are not readily obtainable. The 

 sporophytes of the common E. arvense grows on dry sandy banks, 

 often on railroad embankments. The underground stems send 

 up in spring (April-May) unbranched flesh-colored shoots 5 mm. 



