FERTILIZATION 



small and oblong or lenticular on extrusion, the one passing to 

 the polar nuclei increasing very much in size, the other very 

 little. In Tricyrtis hirta Ikeda 58 found the male nucleus that 

 passes to the polar nuclei showing " enormous change in size 

 and shape " as it passes through the sac. There is usually more 

 or less elongation of male nuclei at the time of discharge or 

 afterward, but in Monotropa uniflora Shibata 54 has seen them 

 elongated when entering the sac, but becoming more nearly 

 spherical as fusion progresses. In the pollen-grain at the time 

 of shedding the generative nucleus stains blue and the tube 

 nucleus red with a combination like cyanin and erythrosin. 

 This reaction is maintained, the male nucleus staining blue 

 even after coming into contact with the nucleus of the egg 

 which stains red ; but as fusion proceeds the male nucleus takes 

 less and less of the cyanin and finally stains with erythrosin 

 like the nucleus of the egg. 



The fusion of the male and female nuclei may be very 

 rapid, as observed by Guignard 48j 53 in Zea and Ranuncula- 

 ceae ; or the two may be long in contact without fusion, as noted 

 by Johnson 37 in Peperomia. The behavior of the chromatin 

 during fusion has received but little attention. Mottier 26 fig- 

 ures the chromatin when the nuclei are partly fused, and the 

 statement is generally current that the nuclei fuse in the resting 

 condition (Fig. 69). In view of 

 the independence of the pater- 

 nal and maternal chromatin dur- 

 ing fertilization in Gymno- 

 sperms, as recently noted by 

 several investigators, it would be 

 well to reexamine the subject in 

 Angiosperms, especially since 

 most observers have paid little 

 or no attention to this phase of 

 the problem. 



Since it has been in connec- 

 tion with fertilization and at- 

 tendant phenomena that the cen- 

 trosome problem has come into 

 greatest prominence, it may not be inappropriate to refer to the 

 subject at this point. Guignard, Schaffner, and others have 



FIG. 69. Lilium candidum. Fusion of 

 sex nuclei ; the synergids appear as 

 dense homogeneous masses. After 

 MOTTIER." 



