Vol. 2] Gardner. — Cytological Studies in Cyanophyceae. 281 



were cutting it in two. In Dermocarpa the nucleus breaks up 

 simultaneously into a large number of daughter nuclei ; the pro- 

 cess is amitotic. 



8. Two kinds of granules have been demonstrated in the Cya- 

 nophyceae cell. One kind, designated as a granules, is located in 

 the nucleus of the vegetative cell in close proximity to the chro- 

 matin (this kind is not present in the mature spore) ; the other 

 kind, designated as (3 granules, may or may not be present in the 

 vegetative cell, but is always present in the mature spore. The 

 age of the plant, physiological conditions, and variation in nutri- 

 tion are probably the determining agencies affecting the presence 

 or absence of the ft granules. 



9. No protoplasmic continuity between the vegetative cells has 

 been demonstrated. 



10. Change in habitat does not produce any marked change in 

 cytological characters. 



11. One of the products of assimilation is glycogen. Sugar is 

 probably one of the first products of assimilation. 



VIII. SUMMARY. 



A new type of nuclear division has been discovered in Der- 

 mocarpa in which the nucleus breaks up simultaneously into a 

 large number of daughter nuclei by a process of amitosis. (See 

 Figs. 33, 34.) 



The present investigation reveals in the Cyanophyceae a se- 

 ries of nuclear structures, beginning with a very simple form of 

 nucleus scarcely differentiated from the surrounding cytoplasm 

 and dividing by simple direct division. From this we pass by 

 very gradual steps to a highly differentiated form of nucleus 

 which in dividing shows a primitive type of mitosis, and in struc- 

 ture approximates the nucleus of the Chlorophyceae and the 

 higher plants. (See Figs. 28, 1 to 5, 40 to 44.) 



In this group of plants the transmission of hereditary quali- 

 ties seems to be accomplished with the greatest precision, with- 

 out the complicated machinery of mitosis. In this connection it 

 may be noted that the lack of sexuality seems in no wise to affect 



