170 SCOTCH PINE. 



Within each is a large nucleated germ cell or oosphere, 

 the part to be fertilized. 



The process of fertilization is as follows : The 

 pollen grains having been lodged in the micropyle 

 upon the apex of the nucellus, the extine is burst and 

 slipped off by the swelling of the intine and its con- 

 tents. By a local growth the intine extends into a 

 tube into which the contents of the larger cell pass by 

 a streaming movement, the smaller cell remaining 

 inert. This pollen tube pushes its way slowly between 

 the cells of the nucellus until it reaches the germ cell 

 in the embryo-sac. Shortly afterward a nucleus almost 

 as large as that of the germ cell appears below the end 

 of the pollen tube. It is to be supposed that it has 

 passed through the wall of the tube, and it is to be 

 regarded as homologous with the body of an an- 

 therozoid. The two nuclei fuse into one, which passes 

 to the end of the germ cell opposite the neck where it 

 gives rise to several four-celled layers, one above 

 another, the lower four of which form the beginning 

 of the embryo. 36 This process of fertilization requires 

 in Pinus sylvestris a little more than a year between 

 the beginning of the growth of the pollen tube and 

 the consummation. 



The fertilized germ cell grows at once into the young 

 plantlet (embryo), as in the fern, but at this stage, 

 unlike the fern, it stops for awhile, and in the passive, 

 well protected condition of a seed may pass a long 

 period before it resumes its growth. This, again, is a 

 special adaptation. All the plants heretofore con- 

 sidered are fully equipped for the dispersion of each 



36 Cf. Strasburger, op. cit, p. 481 et seq. 



