98 MARGARET C. FERGUSON 



give rise to such a nucleus, if we may so denominate it, as that 

 illustrated in the ventral canal-cell of fig. 196 ; although Black- 

 man, judging from such a figure as that portrayed in fig. 194, 

 considers it impossible that the chromosomes of the ventral 

 canal-cell should ever fail to fuse. The nuclear membrane, 

 when present, very soon breaks down, and the chromatic sub- 

 stance becomes scattered throughout the cell (figs. 198-202). 

 This cell immediately preceding and at the time of fertiliza- 

 tion ordinarily forms a deeply staining mass which lies just 

 beneath the neck-cells and above, but in contact with, the egg 

 (figs. 180, plate XVI, 202, plate XVIII, and 213, 215, plate XIX). 

 Rare exceptions to the rapid disintegration of the canal-cell have 

 been observed and will be described in the appendix to this 

 paper. But in the study of several thousand archegonia of 

 Pinus Strobus no instance has been found in which the nucleus 

 of the egg and of the ventral canal- cell were similar in form. 

 The nearest approach to a normal nucleus that has been observed 

 in the ventral canal-cell of this species is that shown in fig. 197, 

 plate XVII. Occasionally this cell is somewhat enlarged and is 

 furnished with a rather scanty amount of cytoplasm in which 

 distinct chromosomes, or chromatic figures of various forms are 

 imbedded. Of the many variations that have been found to 

 occur in the structure of the ventral canal-cell in the mature 

 archegonium but two have been illustrated figs. 199 and 199, 

 plate XVIII. It is probable that in such instances a true nucleus 

 has ever been formed if, indeed, the chromosomes have fused 

 at all. The character of the cell at this time is such as to pre- 

 clude the possibility that a division of this cell is being initiated. 

 There seems to be a definite relation between the structure of 

 the ventral canal-cell and the character of the upper part of the 

 mitotic figure formed in the division of the central cell. This 

 is plainly demonstrated by a comparison of figs. 190 to 197, 

 plate XVII, and 200-202, plate XVIII. Figs. 190, 193, 196 

 and 202 represent an especially interesting series. 



The separation of the canal-cell from the cytoplasm of the 

 oosphere, as Strasburger ('72) and Blackman ('98) have de- 

 scribed in Pinus, is, I believe, due to a shrinkage of the egg- 

 cytoplasm caused by imperfect fixation ; and it is possible that 

 a similar appearance in Cycas, Ikeno ('98), has a like origin. 



