240 Dr. L. Kny on the Structure and 



Tlic anthcriclia of Cei-afoj^teri's thah'ctroides (figs. 8-10) are 

 at the first glance very dissimilar to those oi Anehnia. On 

 closer examination, it appears that tlie difference lies more in 

 the dimensions of the individual parts than in any divergence 

 of structure. Most of the antheridia lierc originate from mar- 

 ginal cells of the proth allium ; only a few are developed upon 

 the lower surface of the frond. In the former, the only one 

 which I have closely traced, the divisions of the mother cell 

 are completed at a period when it scarcely projects perceptibly 

 above its neighbours. 



The first septum is usually unsymmetrical and strongly 

 curved. It is attached on the one side to the free outer Avail 

 of the mother cell, and on the other to one of the side walls 

 which separate this from the neighbouring cells. The lower 

 cell thus cut off of course extends only on one side to the free 

 margin of the prothallium (figs. 9 a, 10). Unfortunately I have 

 no direct observation of the next step in division. From the 

 mature state, in conjunction Avith the undoubtedly ascertained 

 process of development in Aneimia hirta, I think I may con- 

 clude that here also the first-formed Avail is folloAved by a 

 Avatchglass-shapcd membrane, AA'hicli separates an inner cell 

 of the form of a biconvex lens from an outer shallow bell- 

 shaped cell. In the latter, as in Aneinna, a funnel-shaped 

 septum Avidening upwards Avould then be produced, isolating 

 the opercular cell from the ring cell. The latter here always 

 remains short and at the same time slightly curved doAvnAvards. 

 This, combined Avith the Avant of a true peduncular cell, is 

 Avhat chiefly causes the peculiar habit of the antheridium of 

 Cerafojyferis. 



Divergences from the structure just described but seldom 

 occur, llie commonest is, that the first septum attaches itself 

 symmetrically to the tAvo lateral Avails (fig. 9 h) instead of only to 

 one of them. Only in the rarest cases have I observed mature 

 antheridia in Avliich the separation of the ring cell and the 

 opercular cell had been omitted, and in Avhich, therefore, the 

 special mother cells Avere enclosed in a lenticular space be- 

 tAveen tAvo cells. 



Asj)Ieni'um alatum possesses antheridia in which the nucleus 

 is usually enclosed by two superimposed ring cells (PI. VI. 

 figs. 14 & 15). The operculum, as in Aneimia hirta and 

 Ceratopteris thalictroides, is unicellular. A peduncular cell 

 is not always present (figs. 11, 14, & 15). 



On the Aveakly prothallia examined by me (Avhich had been 

 much croAvded during groAvth) the antheridia Avere developed 

 chiefly on the surface of the frond, frequently in such abun- 

 dance that every cell bore an antheridium. They Avere pro- 



