48 MARGARET C. FERGUSON 



pollen-tube the tube-nucleus, as shown by Strasburger ('92) 

 moves away from the antheridial cell and into the pollen-tube 

 (figs. 75, 76, plate VII). According to Coulter and Chamber- 

 lain ('01, page 92), the tube-nucleus does not enter the tube 

 until the following April. That the tube-nucleus should at once 

 loose its association with the antheridial cell and accompany the 

 growing point of the pollen-tube is exactly what we should 

 expect from what we know, through the investigations of 

 Haberlandt ('87) and others, regarding the relation of the 

 nucleus to growth ; and, also, judging from the standpoint of 

 analogy, from the remarkable migrations of the tube-nucleus in 

 order to be near the growing point of the pollen-tube in Cycas 

 (Ikeno '98) and in Zamia (Webber '01). 



Division of the Antheridial Cell. — Strasburger ('92) described 

 the antheridial cell in Pinus sylvestris as remaining unchanged 

 until the archegonia are formed in the following spring. Dixon 

 states that it divides about a month before fertilization, but from 

 a careful reading of the text one is given the impression that this 

 was an inference on his part rather than a demonstrated fact, as 

 he did not study material that was preserved earlier than April 

 24 and did not find the karyokinetic figure for this division. 

 And, in so far as I am aware, this mitosis has not been observed 

 in Pinus. Strasburger describes and figures it in Picea while 

 the pollen-grain is still within the anther.^ 



I have found great variation in the time at which the anther- 

 idial cell divides, not only in different species but in the same 

 species. It is rather interesting that Pinus Strohus, which 

 invariably lags somewhat behind the other species in all 

 other developmental phases studied, is remarkably precocious 

 as regards this step. Figs. 78, 80, and 81 were all taken 

 from material of Pinus Strohus which was collected and pre- 

 served on August 4, 1898, barel}' two months after pollina- 

 tion. In the same material, other pollen-grains were observed 

 in which the division of the antheridial cell had not yet taken 

 place ; but in material fixed somewhat later it was rarely found 

 undivided. The division of this cell has not been observed in 

 Pinus austriaca, but two cells have been found in the pollen- 

 grain in the middle of November and in February, and in such 



' See note at close of appendix. 



