342 



GENERAL MORPHOLOGY OF PLANTS 



were developed. The prominent leaves are in two lateral rows, 



but there is an inconspicuous third row on the underside. The 



stems are creeping or ascending. They are attached to the 



soil, to logs, or tree trunks, by 



rhizoids. They are sometimes 



mistaken for mosses.* Many 



of the foliose liverworts grow 



in moist situations, as on the 



trunks of trees in the forest or 



in groves, where in dry weather 



Fig. 303. Fig. 304. 



Section of developing sporogonia of Foliose liverwort, male plant showing 



Marchantia; nt, nutritive tissue of game- antheridia in axils of the leaves (a junger- 

 tophyte; st, sterile tissue of sporophyte; sp, mannia). 

 fertile part of sporophyte; va, enlarged 

 venter of archegonium. 



they would be in danger of being killed were it not for some 

 special peculiarity in their form, etc. One of these (Frullania) 

 has oval leaves closely crowded and overlapping each other on 



* Most mosses are, however, more or less erect; the leaves are in three 

 distinct rows and equal in size, except in certain forms. Vegetative stems 

 of Mnium, one of the mosses, are creeping, and there are two prominent 

 lateral rows resembling a liverwort. So in Fissidens, another moss, the 

 prominent leaves are in two lateral rows and the stems are more or less 

 inclined or creeping as in some liverworts. The leaves of liverworts always 

 consist of a single layer of cells, while in the mosses there is a midrib of 

 more than one cell in thickness extending part way into the base of the leaf, 

 or entirely through the leaf, except in the peat mosses. 



