270 Phillips on a Comparative Study of the 



withstanding chemical reagents, and therefore resemble the 

 cutin of the higher plants, but in chemical and optical 

 characters have no relation whatever to it. (3) The walls 

 of the heterocysts, on the other hand, consist wholly of 

 cellulose. (4) A substance which has the nature of pectine 

 (staining with ruthenium red) is concerned in the forma- 

 tion of the gelatine slime coverings. (5) The protoplast 

 is divided into a peripheral layer carrying the coloring 

 matter and a central colorless portion. A colorless hyalo- 

 plasm layer usually surrounds the peripheral portion of the 

 protoplast under the cell wall, and a similar layer usually 

 separates it from the central body. (6) Many granules 

 containing the coloring matter are packed into the periph- 

 eral protoplasm, giving it the appearance of a homo- 

 geneous layer, which, however, by the use of concentrated 

 magnesium sulphate solution and Zeiss' apochromatic 

 lenses, may be easily resolved into its constituent granules. 

 These granules contain the chlorophyll and phycocyanin 

 blended together in one and the same coloring body, so that 

 we have an association of coloring matter similar to that 

 found in the Rhodophycese (54). (7) These granules 

 which carry the coloring matter are regarded as the chroma- 

 tophores and are therefore designated as "Cyanoplasts." 

 They are connected by fine protoplasmic threads with the 

 peripheral protoplasm and with a pocket-like layer of proto- 

 plasm surrounding the nucleus similar to the pellicle sur- 

 rounding the nucleus of Spirogyra. (8) Starch or any 

 starch-like substance is lacking in the Cyanophyceae, but gly- 

 cogen is present, which is the first assimilation product of 

 these plants, because it appears and disappears according as 

 the plant is grown in light or darkness. (9) Beside the 

 cyanoplasts, the peripheral cytoplasm contains two other 

 enclosures, the albuminous crystalloids (cyanophycin granules 

 of other writers) , and the slime vacuoles (slime balls of other 

 authors). These enclosures are always found in the peri- 

 pheral protoplasm of the cell. ( 10) The albuminous crystal- 



