98 MORPHOLOGY OP SPERMATOPHYTES 



bottom is nearly or quite reached. In Taxus there is the same 

 passing of the paired nuclei to the bottom of the egg for fusion, 

 and they are also reported as being of the same size. Perhaps 

 it is well to call attention to the fact that two free nuclei from 

 the early divisions of the fusion nucleus might be mistaken for 

 male and female nuclei unless the latter had been previously 

 observed and their great difference recognized. These free 

 nuclei are of the same size and pass to the bottom of the oospore. 

 It is also very possible that in some cases the ventral canal cell 

 is fertilized rather than the egg ; and there are some grounds for 

 believing that the nuclei of the ventral canal cell and of the egg 

 may fuse, suggesting what has been observed among animals in 

 cases of parthenogenesis (Wilson, loc. cit., pp. 280-283). 



IV. THE EMBRYO 



The first adequate account of the development of the embryo 

 in Conifers was that given by Strasburger in 1872.^'' Later 

 the same author ^* published more fully upon the subject, and 

 several investigators since have touched upon the embryogeny 

 of Conifers ; but the whole subject is in need of more detailed 

 investigation. While the earlier stages of the embryo are fairly 

 well known, our knowledge of the development of the embryo 

 .proper is little more than an outline. We have obtained a com- 

 plete series of the early stages in Pinus Laricio, and from it the 

 following account is written. 



1. Development of Proemhryo. — The fusion nucleus retains 

 its central position in the cytoplasm of the oospore (Fig. 76, A), 

 and, beginning to divide, organizes the largest spindle of the 

 free nuclear series (Fig. 77), as in Cycads and Ginkgo. The 

 axis of this spindle is always inclined to the long axis of the 

 archegonium, and its fibers are not at all convergent, resulting 

 in a broad rectangular outline. The two daughter nuclei are 

 very small at first, but increase rapidly in size, and then 

 simultaneously divide. The four free nuclei which are 

 formed by this second division are at first very small, but 

 increase in size both through vacuolation and by taking in 

 substance (Fig. 76, B). When the four nuclei have reached 

 their full size, they begin to move toward the base of the spore, 

 and at this time show an investment of strong fibers, which 



