No. 4S4-] STUDIES ON THE PLANT CELL. 729 



but there is found instead one large, broad poled spindle. (See 

 Fig. 5 ^.) A cell wall is formed between the two daughter 

 nuclei (Fig. 8 d ) which divide again after a very short period of 

 rest, the two spindles lying at right angles to one another. The 

 poles of the spindles are rather blunt, and there are no centro- 

 somes or centrospheres in either mitosis. The four-rayed struc- 

 ture of prophase must be regarded as preliminary to spindle 

 formation because the chromosomes are not ready for distribu- 

 tion, and when that period arrives the structure has been re- 

 placed by the true spindle of the first mitosis. These facts led 

 me to question Farmer's account of mitotic phenomena in Palla- 

 vicinia and his conception of the " quadripolar spindle," and I 

 suggested that this structure might prove to be a phenomenon of 

 prophase, a view to which Farmer (:oi) has taken exception in 

 a criticism of my results. 



Recent investigations of Moore (: 03) on Pallavicinia are flatly 

 contradictory to the conclusions of Farmer for Pallavicinia 

 decipiens and support my suggestions. Moore finds that there 

 are two mitoses in the spore mother-cell of Pallavicinia lyellii, 

 the second (Fig. 12 c, d) following immediately upon the first 

 {Fig. 12 b), each with bipolar spindles and without centrosomes. 

 The chromosomes, eight in number, appear in the usual way 

 with each mitosis (Fig. 12 c, d). There is no "quadripolar 

 spindle" in Farmer's sense, no quadrupling and simultaneous 

 distribution of the chromosomes. The prophases preceding the ' 

 first mitosis present a tetrahedral form as is shown in Fig. 12 a. 

 This is accentuated by the fibrillae which gather at the points 

 to make a four-rayed structure extending into the lobes of the 

 spore mother-cell. This condition is identical with similar stages 

 in Pellia and in other leafy liverworts, and is a feature to be 

 expected from the fact that the spindle fibers develop chiefly or 

 wholly externally to the nuclear membrane in a rather crowded 

 region of the cell. The nucleus at this time is unquestionably 

 in prophase as shown by the undifferentiated chromosomes and 

 because this stage passes immediately into a bipolar spindle of 

 the normal type (Fig. 12 b). It seems very probable that 

 Farmer was mistaken in his conclusions for Pallavicinia decipi- 

 ens, and that the mitoses in the spore mother-cell of this form 



