LIFE HISTORY OF PINUS 1 29 



of the egg at the time of the division of the two segmentation- 

 nuclei. I have said "attempt to divide," for no instance has 

 been observed in which the division of these nuclei has extended 

 beyond a late prophase. A bipolar spindle, with the chromatic 

 segments scattered irregularly upon it, represents the most ad- 

 vanced stage which has been seen in the division of the smaller 

 sperm-nucleus (fig. 259, ^, plate XXIII). (During sectioning, a 

 rupture was made in the cytoplasm at one end of this spindle 

 so that the upper pole has been separated mto two.) The stalk- 

 cell still persists at this late date (fig. 259, b, plate XXIII), 

 and in another section of the series (fig. 259, <?), a second 

 mitotic figure appears. This evidently represents the tube- 

 nucleus. The achromatic part of the figure presents the ap- 

 pearance of a normal bipolar spindle, but, the chromatic spireme 

 has not become homogeneous and probably would not have 

 developed further. In some cases a well-developed spireme is 

 formed in the upper part of the ^^^i but no achromatic threads 

 become apparent (fig. 257); again, a nucleus seems to have 

 been entirely resolved, during its disintegration, into achromatic 

 fibers. As above stated, in no case observed did the division 

 of these nuclei reach telokinesis, but at some point in the devel- 

 opment prior to such a late stage, activity ceased and disinte- 

 gration of the nuclear elements took place. Murrill ('00) ob- 

 served a similar figure, which he interpreted as the smaller 

 sperm-nucleus, in the upper part of the fertilized o.^^ in Tsiiga} 



It might be suggested that these division-figures result from 

 the conjugation of the nucleus of the ventral canal-cell with the 

 smaller sperm-nucleus. There is no evidence that such is the 

 case, and I am convinced that they could not have had such an 

 origin. In an examination of many hundred archegonia just 

 before fertilization, but one ventral canal-cell containing a nor- 

 mal nucleus has been observed. Shall we, then, conclude that, 

 in a far less number of preparations representing stages imme- 

 diately following fecundation, fifty or more instances occur in 

 which the nucleus of the ventral canal-cell has conjugated with 

 another nucleus and subsequently divided? 



It is generally recognized, especially by cytologists on the 



1 See note at close of Appendix. 



