276 MOSSES AND FERNS chap. 



The sporophyte is in most species either aquatic or amphibious, 

 but a few species are terrestrial. They are very much ahke in 

 appearance, having a very short stem whose upper part is 

 completely covered with the overlapping broad bases of the 

 leaves, which themselves are long and rush-like, so that the 

 plant in general appearance might be readily taken for an 

 aquatic Monocotyledon. The roots are numerous and 

 dichotomously branched. The stem grows slowly in diameter, 

 and the older ones show two or three vertical furrows that unite 

 below, and as the stem continues to grow these furrows deepen, 

 so that the old stem is strongly two or three lobed. In the 

 furrows the roots are formed in acropetal succession. The 

 leaves are closely set and expanded at the base (Fig. 144) into 

 a broad sheath, with membranaceous edges. Just above the 

 base of each perfectly -developed leaf is a single very large 

 sporangium, sunk more or less completely in a cavity (fovea), 

 which in most species is covered wholly or in part by a 

 membranaceous indusium (velum), and above the fovea is a 

 scale-like outgrowth of the leaf, the ligula. The spores are of 

 two kinds, borne in separate sporangia. The outer leaves of 

 each cycle produce microspores, the inner ones macrospores, 

 many times larger than the former. The innermost leaves, 

 which are not usually perfectly developed, are sterile, and 

 separate one year's growth from the next. In some of the 

 land forms, e.g. I. hystrix, these sterile leaves are very much 

 reduced, and form spine-like structures. 



The Gainetophyte 



The germination of the microspores was studied by 

 Hofmeister,^ and later by Millardet ^ and Belajeff,^ the later 

 writer differing in some essential particulars from the earlier 

 observers. The two former studied /. lacustris, and Belajeff 

 /. setacea and /. M alinverniana, which do not seem to differ, 

 however, from /. echinospora, which was investigated by the 

 writer. The microspores of all the species are bilateral, and are 

 small bean-shaped cells with thick but in most species nearly 

 colourless walls. The epispore sometimes has spines upon it, 

 but in /. echinospora var. Braunii the surface of the spore is 

 nearly smooth. In this species the spores begin to ripen in the 



1 Hofmeister (i), p. 341. ^ Millardet (i). ^ Belajeff (i). 



