No. 454-] STUDIES ON THE PLANT CELL. 729 



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

 Fig. 5 e.) 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 " quadri polar 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 



