262 



SEEDLESS PLANTS 



STUDY OF A BRYOPHYTE 



Material. — Any of the common thalloid or flat-bodied liverworts. 

 They can generally be found growing with mosses on wet, dripping rocks 

 and the shady banks of streams, and are easily recognized by their flat, 

 spreading habit, which gives them the appearance of green lichens. 

 Marchantia polymorpha (Fig. 500), one of the largest and best speci- 

 mens for study, is common in shady, damp ground throughout the north- 



500. — Umbrella liverwort {Marchantia polymorpha) ; portion of a thallus about 

 natural size, showing dichotomous branching: /,/, archegonial or female recep- 

 tacles ; r, rhizoids. 



ern States. Lunularia, a smaller species that can be recognized by 

 the little crescent-shaped receptacles on some of the divisions of the 

 thallus, is abundant in greenhouses almost everywhere, on the floor, or 

 on the sides of pots and boxes kept in damp places. Specimens of this 

 can be procured by city classes, but the spore-bearing receptacles are 

 seldom or never present, the species being an introduced one and possi- 

 bly rendered sterile by changed conditions. Marchantia polymorpha 

 is the specimen described in the text, but any allied species will do. 



