No. 463.] STUDIES ON PLANT CELL. VI. 463 



ments, substances of great service, although possibly not abso- 

 lutely necessary to the successive metabolic processes which 

 characterize growth and development. But the _fact remains 

 that we have in the chromosomes the only new morphological 

 elements. And the progress of research seems ever to 

 strengthen the general view that in the chromosomes are 

 contained the directive rudiments of development and that 

 they are the bearers of hereditary principles. Nuclear studies 

 on apogamous forms will certainly prove of great interest in this 

 connection. We have reason to expect some very important 

 results from thorough cell studies on apogamy and apospory. 



The best developed theory of fertilization in plants is that of 

 Strasburger and a statement of his views should precede any 

 comments of other authors. Strasburger has written much on 

 the phenomena of fertilization ; important considerations may be 

 found in his papers of '94a, b, '9/c, : ooa, b, :oi, and : O4a. 

 Strasburger points out that the protoplasm of the egg is pre- 

 dominately trophoplasmic in character because of the propor- 

 tionately very large amount of cytoplasm with granular inclusions 

 that are evidently food material or the products of metabolism. 

 On the other hand the cytoplasm of the sperm contains rela- 

 tively little trophoplasm and much kinoplasm, especially when 

 the sperm is a ciliated cell with a large blepharoplast. As 

 Strasburger conceives kinoplasm to be the active substance of 

 spindle formation, -he concludes that the sperm might bring to 

 the well nourished egg, rich in trophoplasm, the substance neces- 

 sary to start the mechanism of mitosis. In its broad aspects 

 this view is very similar to the celebrated theory of Boveri, 1887, 

 that the spermatozoon supplied the animal egg with the centro- 

 some which is conceived as necessary to start mitotic processes 

 and that the egg is powerless to divide before fertilization 

 because it lacks such a structure. 



Another feature of Strasburger's views (advanced in his paper 

 of : oob) appears to have grown out of the discovery of the so 

 called "double fertilization " in the embryo-sac and other nuclear 

 fusions whose sexual significance is not clear, together with the 

 phenomena of parthenogenesis as produced experimentally in 

 many studies of recent years. Strasburger considers that two 



