62 



MOSSES AND FERNS 



CHAP. 



capsule now contains a mass of isolated cells of two kinds, 

 globular sporogenous cells and elongated elaters. The former 

 now. divide into four spores, but before the nucleus divides 

 the division of the spores is indicated by ridges which project 

 inward and divide the cavity of the mother cell almost com- 

 pletely. 



With the first divisions in the embryo the venter of the 

 archegonium, which before was only one cell thick, divides by 

 a series of periclinal walls into two layers of cells, which later 

 undergo further divisions, so that the calyptra surrounding the 



A 



Fig. 23. — Fimbriaria CalifoTnica (Hampe). A, Young, B, older embrj'o in median section. A, 

 X300 ; B, xioo; C, upper part of a sporogonium, after the differentiation of the archesporium, 

 X200. 



I 



older capsule may consist of four or more layers of cells. The 

 neck of the archegonium remains unchanged, but the tissue of 

 the thallus below the archegonium grows actively, and surrounds 

 the globular foot, which has grown down into the thallus for 

 some distance, and only the capsule remains within the 

 calyptra. This large growth of the foot is at the expense of 

 the surrounding cells of the thallus, which are destroyed by its 

 growth, and through the foot nourishment is conveyed from the 

 thallus to the developing capsule. That is, the sporogonium is 

 here a strictly parasitic organism, growing entirely at the 

 expense of the thallus. 



