REPRODUCTIVE CELLS. 



HI 



being, in fact, shot out by the effect of the elastic recoil of the 

 annulus, and, after falling upon a suitable substratum, each spore 

 germinates. The outer wall of a mature spore is much wrinkled 

 in the genus Aspidium (in the figure this is not represented). 



. 107. — Details ^DIAGB.\MMATIc) ov the Eeproductive Cycle in 

 Aspidium (Homosporous Fekxs). — 1. A mature sporangium, showing 

 the spore-chamber with spores inside, the stalk, and the curved 

 annulus. 2. A single spore. 3. Germination of the spore by the 

 splitting of the thick outer wall and protrusion of the cytoplasm 

 contained in the thin inner wall. 4. An antheridium from the under 

 surface of a, mature prothallus ; a few mother-cells of the anthero- 

 zooids are seen in the central cavity. 5. A single antherozooid, 

 showing the rounded head with vesicle attached, and the tail, at 

 the end of which are the cilia. 6. An oogonium sunk in the 

 under surface of the prothallus. Note the oogonium proper con- 

 taining the oosphere, and the canal, in which are the canal-cells. 

 7. The first two divisions of the oospore. 



