398 MOSSES AND FERNS chap. 



much like that of some of the Hymenophyllacese and Cyathe- 

 acese. 



The Gametophyte 



The first account of the development of the sexual stage 

 of the Salviniacese that is in the least degree accurate is Hof- 

 meister's ( i ) , who made out some of the most important points 

 in the development of the female prothallium. Pringsheim's 

 (i) classic memoir on Salvinia added still more, as well as 

 Prantl (4) and Arcangeli ( i ) , but none of these observers were 

 able to follow accurately the earliest divisions in the germinat- 

 ing macrospores. Berggren's (2) account is the only one on 

 the female prothallium of Azolla, except a paper by the writer, 

 but Belajeff (4) has given an excellent account of the germina- 

 tion of the microspores. 



The Male Prothallium 



The microspores at maturity are embedded firmly in a mass 

 of hardened protoplasm, which in Salvinia fills the whole spo- 

 rangium, but in Asolla is- divided into separate masses, "massu- 

 lae." The wall of the sporangium in Azolla decays and sets these 

 free in the water, but in Salvinia the wall of the sporangium is 

 still evident when the germination takes place. In the latter the 

 young prothallium grows into a short tube, whose basal part is 

 separated as a large vegetative cell, from whose base later, Bela- 

 jeff states, a small cell is cut off. The upper cell becomes the 

 antheridium. In it is first formed in most cases an oblique 

 wall, which Belajeff states is always followed by another similar 

 one, which forms a central sterile cell separating the two groups 

 of sperm cells. This cell, however, did not occur in the speci- 

 mens studied by me, where the two groups of sperm cells were 

 usually in immediate contact (Fig. 233, E). From each of the 

 upper cells peripheral cells are cut off, but they do not com- 

 pletely enclose the sperm cells, which are in contact with the 

 outer wall of the antheridium. A cover cell corresponding to 

 that in the ordinary Fern antheridium is more or less conspicu- 

 ous. Each of the central cells divides by cross-walls into four, 

 and there are thus eight sperm cells in the ripe antheridium. 

 The spermatozoids of Salvinia have about two complete coils. 



