VoL - 2] Gardner. — Cytological Studies in Cyanophyceae. 273 



so closely united to the chromatin, while the ft granules are prob- 

 ably accumulated food material. 



In the homocysteae the ft granules are located most frequently 

 along the cross-cell walls, the location, however, being a specific 

 character. In some species they are distributed quite evenly 

 throughout the cytoplasm, and in a single instance (Symploca 

 Muscorum, Fig. 13) they are scattered among the a granules in 

 the nucleus, at least wasserblau which invariably differentiates 

 them in other species stains some granules blue within the nu- 

 cleus. 



They arise de novo. Their development may be watched in 

 Lyngbya aestuarii (Fig. 35), in which they are arranged along 

 the cross-walls only. As the new wall grows in from the side, 

 soon the ft granules appear. They increase in size and number 

 as the cell grows older. Fig. 39 represents their arrangement 

 and occurrence in Oscillatoria splendida. Fig. 15 represents 

 them in end view of Oscillatoria margaritifera stained with was- 

 serblau, and Fig. 14 represents the first species first stained with 

 thionin, then counterstained with wasserblau. The a granules 

 are red and the ft granules are blue. They are both represented 

 in the same plane, but the a granules are, in end view, below the 

 ft granules ; that is, they are within the nucleus while the ft gran- 

 ules are along close to the cross-cell wall. This same differentia- 

 tion is shown in Fig. 13, in which case the a granules are stained 

 red with Ehrlich's haematoxylin. 



(c) THE CYTOPLASM. 



The space between the nucleus and the cell-wall is occupied 

 by the cytoplasm, the structure of which, as would be expected, 

 varies considerably in its finer details in different species, and 

 also in different cells of the same species. 



Much controversy has arisen over the shape of the achromatic 

 portion of the nucleus. Under a certain treatment in some spe- 

 cies it seems to extend as a distinct substance out into the general 

 cytoplasm by means of fine radiating arms. My investigation has 

 not yet been conclusive on this point. The stains which best dif- 

 ferentiate the chromatin do not differentiate the achromatic por- 



