240 Dr. L. Kny 0)i the Struciure and 



Tlic antlicridia of Cerafojjten's thah'ctroiJes (iigs. 8-10) are 

 at the first glance very dissimilar to those oi Anct'mia. On 

 closer examination, it ap]iears that the difl^crcnec lies more in 

 the dimensions of the individual jiarts than in any divergence 

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

 ginal colls of the prothallium ; only a few arc developed upon 

 the lo-wer surface of the frond. \n 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 se})tum is usually unsymmetrical and strongly 

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

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

 which separate this from the neig]d)ouring cells. The lower 

 cell thus cut oif 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 with the undoubtedly ascertained 

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

 clude that here also the first-formed wall is followed by a 

 watchglass-shapcd membrane, which separates an inner cell 

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

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

 septum widening upwards would then be produced, isolating 

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

 remains short and at the same time slightly curved downwards. 

 This, combined with the want of a true peduncular cell, is 

 what chiefly causes the peculiar habit of the antheridium of 

 Ceratojjten's. 



Divergences from the structure just described but seldom 

 occur. The commonest is, that the first septum attaches itself 

 symmetrically to the two lateral walls (fig. 9 h) instead of only to 

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

 antheridia in which the sejiaration of the ring cell and the 

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

 special mother cells were enclosed in a lenticular space be- 

 tween two cells. 



Asjjienium (datum possesses antheridia in which the nucleus 

 is usually enclosed by two sujyerimjwsed 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 (which had been 

 much crowded during growth) the antheridia were developed 

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

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



