204 CAT.IFORNIA ACADEMY OF SCIENCES. 



EXPLANATION OF FIGURES. 



ri.ATE III — THE MICROSPORE. 



All figures magnified about 300 times, and all e\ce]it figures i to 3 and 22 to 

 24, microtome sections. 



Figure i. Ripe fruit of Marsilia vestita twice the natural size. 



Figure 2. A fruit which has been artificially opened and placed in water, x 

 I y^. X, the valves of the fruit; m, the mucilaginous body to which the sori 

 are attached. 



Figure 3. Afresh microspore seen from the top. 



Figure 4. Section of an ungerminated microspore; n, nucleus. 



Figure 5. Section through the wall of a microspore x 600. i, 2, 3, the 

 three layers of the wall. 



Figure 6. Surface views of the epispore; a, x 300, b, x 600. 



Figure 7. Section of spore showing first signs of germination. The nucleus 

 has moved to one side, and the granular protoplasm has collected in the middle. 



Figure 8. Section of a spore in which the first division is completed; x, the 

 vegetative cell. 



Figure 9. A somewhat more advanced stage in longitudinal section; w, the 

 basal cell of the antheridium. 



Figure 10. Two longitudinal sections of n s])ore in whicli no basal cell was 

 formed in the antheridium. 



Figure 11. Cross section of young antheridium. 



Figures 12 to 16. Successive stages in the development of the antheridium seen 

 in longitudinal sections, .r, the vegetative cell of the prothallium; /, the 

 peripheral cell of tlie antheridium; d, the cover cell of the antheridium. 



Figures 17 to 19. Similar stages of the antheridium seen in cross section. 



Figure 20. Full-grown male prothallium and antheridium; a, b, in longitu- 

 dinal section c, cross section; d, side view of a group of sperm cells. 



Figure 21. Two sperm cells from a prothallium eight hours old showing the 

 beginning of the formation of the spermatozoids; x 600. 



Figures 22 to 24. Free spermatozoids x 600. Figure 22, a the active sperma- 

 tozoid; b, one which has come to rest and the l^ody become extended; 23 and 

 24, two stages similar to that shown in 22 b, but with the cilia omitted. 



PLATE IV — THE MACROSPORE. 



All the figures drawn from microtome sections fixed with chromic acid and 

 stained with alum-cochineal and IMsmarck-brown. Unless otherwise stated 

 magnified about 150 times. 



Figure i. a, longitudinal section of ungerminated macrospore, x 60, n, nu- 

 cleus; b, portion of the wall x 300. 



Figure 2. Upper part of spore contents from a spore which has lain for one 

 hour in water. 



Figure 3. Upper part of spore two hours old. 



Figure 4. Nucleus of similar spore, x 300. 



