2 9 8 BOTANICAL GAZETTE [may 



prothallia, in which, at least up to the appearance of the archegonium 

 initial, the walls are formed somewhat regularly, being more or less 

 perpendicular or parallel to the surface of the prothallium. 



SPERMATOGENESIS 



Every apogamous prothallium bears antheridia in profusion, the 

 antheridium initial being formed earlier than in normal prothallia 

 of similar size. The formation of the primary spermatogenous cell, 

 which takes place as in normal prothallia, is studied more readily 

 on account of the comparatively large size. The mitoses from the 

 primary spermatogenous cell to the formation of spermatids and 

 sperms showed no deviation from spermatogenesis in normal pro- 

 thallia. During these mitoses 64 or 66 chromosomes could always 

 be counted. The peculiar structures which were observed within 

 the cytoplasm in the primary spermatogenous cell of the normal 

 prothallia were also present here, but they seemed to be undoubtedly 

 plastids. 



The sperms are actively motile and are attracted by 0.01 per 

 cent, solution of sodium malate. From the similarity of the genetic 

 development, morphological structure, and characteristic response to 

 the chemotactic stimulus, it is clear that sperms formed in such pro- 

 thallia can function when conditions permit. 



An irregularity in the axis of mitoses was observed during the 

 cell divisions within the antheridium: in most cases the first wall 

 which divides the primary spermatogenous cell vertically is followed 

 by two or three vertical walls parallel to the first, before any trans- 

 verse division takes place. 



OOGENESIS 



While antheridia and functional sperms are formed in abundance, 

 archegonia are rare in these prothallia. The power of forming 

 archegonia seems to be almost suppressed; and the cushion region 

 where archegonia generally arise is very often covered with antheridia 

 instead of archegonia. In extremely rare cases, however, there 

 appears an archegonium initial, from which a central cell is cut off 

 as in normal prothallia. The central cell either remains without any 

 further division and imbedded below a superficial cell, or develops 

 into canal cells and an egg cell, the projecting neck cells being poorly 



