No. 466.] STUDIES ON PLANT CELL. VIII. 719 



out by the work of Farmer whose accounts of centrosomes and 

 centrospheres in the germinating spores of Pellia and within 

 the spore mother-cell of various liverworts, together- with his 

 account of a " quadripolar spindle ' ' made it evident that the 

 group offered some very interesting cytological problems. They 

 led the author to the study Anthoceros (Davis, '99) and Pellia 

 (Davis, :oi), investigations which have been followed by Van 

 Hook (: oo) on Marchantia and Anthoceros, Moore (: 03) on 

 Pallavicinia, Chamberlain (: 03) and Gregoire and Berghs (:O4) 

 on Pellia, while Ikeno (: 03) has studied the processes of sperma- 

 togenesis in Marchantia. 



My studies on sporogenesis in Anthoceros and Pellia led me 

 to conclude that the processes of spindle formation did not 

 differ in any essentials from those in the pteridophytes and sper- 

 matophytes. There are present two successive mitoses and the 

 spindles are formed from a surrounding mesh of fibrillae devel- 

 oped from the kinoplasm associated with the nuclear membrane 

 and without achromatic centers (centrospheres or centrosomes). 

 They exhibit clearly the free fibrillar type of spindle formation 

 although in somewhat simpler form than in the pteridophytes 

 and spermatophytes. The poles of the spindles generally end 

 bluntly in areas of granular kinoplasm but these seem to me too 

 indefinite in form to deserve the designation of centrospheres 

 and such granular inclusions as may be present are too variable 

 in number and position to be termed centrosomes. There is 

 clearly present in Pellia during the prophase of the first mitosis 

 a four-rayed achromatic structure which is later replaced by a 

 typical bipolar spindle. This four-rayed kinoplasmic structure 

 is evidently the same as Farmer's " quadripolar spindle " which 

 he described as associated with a simultaneous distribution of the 

 chromatin in Pallavicinia to form at once four daughter nuclei. 

 I was led to doubt this account and to suggest that the "quad- 

 ripolar spindle " might prove to be simply a phenomenon of 

 prophase associated with the peculiar four-lobed structure of 

 the spore mother-cell in the Jungermanniales. I stated my 

 belief that the distribution of the chromosomes during sporo- 

 genesis in all liverworts would be found to take place through 

 two successive mitoses after the usual manner. Moore (: 03) 



