1 66 



ARCHEGONIATES. 



that of my own observations, and from the work of Chamberlain ('99) 

 on Pinus laricio and Murrill (1900) on Tsuga canadensis, it seems 

 that a similarly constructed nucleus is present in these species. In 

 Pinus strobus (Ferguson, 'or) the structure of the egg-nucleus may 

 vary from a most delicate network bearing minute granules to an inter- 

 rupted, imperfect reticulum composed of large, irregular, diffusely- 



c 



FIG. 69. The fusion of the sexual nuclei in Pinus sylvestris. (After Blackman.) 



A, egg cell showing male nucleus (a) entering female nucleus (6). 



B, later stage in the fusion of the sexual nuclei, parental chromatin masses separate. 



C, male and female nuclei fused, multipolar spindle formed. 



staining elements. It has one large, vacuolate nucleolus and a variable 

 number of small nucleoli. 



The sexual nuclei of Pinus on coming together are in the resting 

 condition, and as in Cycas, Ginkgo, and Zamia the male nucleus 

 penetrates bodily into the female nucleus. Here also the male nucleus 

 seems to press with some force against the membrane of the egg-nucleus, 

 thereby forming a concave depression in the latter (Fig. 69, A). 



