458 BOTANICAL GAZETTE [December 



that of the body cell very dense. The tube nucleus begins to dis- 

 integrate before the pollen tube emerges from the exine; usually 

 during the pollen tube stage it appears only as an irregular aggre- 

 gation; seldom, if ever, does it enter the egg. 



A number of gametophytes have been found similar to that 

 shown in fig. 2. The first division has cut off a polar (" prothallial ") 

 cell which later has disintegrated; the second division has given 

 rise to two equivalent cells; which of the two might have been 

 regarded as prothallial, under other circumstances, is impossible to 

 determine. Evidently there are two antheridia. The conclusions 

 based on a study of Picea (9), namely, that under favorable condi- 

 tions any of the cells resulting from the three primary divisions of 

 the male gametophyte may be antheridial, are supported by the 

 facts as found in Abies. 



The period of time between pollination and fertilization is from 

 four to five weeks. During the greater part of this time the pollen 

 grains lie dormant on the nucellus, or lodged in the micropyle. The 

 course of the pollen tube is direct, and the motion rapid. Although 

 the rate is difficult to determine, it is believed that the passage 

 time of the pollen tube does not exceed two days, and probably may 

 be measured in hours. 



Fertilization of the ventral canal cell 



The division of the central cell to form the egg and the ventral 

 canal cell is similar to that in Pinus (figs. 7, 8, 9; compare, 3, 5, 

 6, 19); the nuclei formed are similar in size and form. The egg 

 nucleus at once begins to move toward the center of the egg cyto- 

 plasm (fig. 7). What the attractive force may be is unknown, but 

 the nucleus of the ventral canal cell responds to the same force and 

 moves in the same direction. This nucleus breaks through the 

 cell wall and enters the cytoplasm of the egg (figs, n, 12); here it 

 increases in size until it reaches a length, in some cases of 80 n, 

 which is approximately one-half of the greatest length attained by 

 the egg nucleus. The structure of the ventral nucleus is very simi- 

 lar to that of the egg, which will be described later. The latter is 

 surrounded by a dense granular layer which is not present in the 

 case of the former. 



