42 Ol i vo, Mitotic division of the miclci of the Cyaiiophyceae. 



Y\<X. iV,]. T\V(i vaciiolar formations arc secn in tlie central i)n(ly. Tt is 

 possible tluit tliese are slinie globales. The aciiroiiiHtin is lici-e niure dis- 

 tiuctlv visible tlian iu ii«;-. ;52. 



Fig. 34. A longitndinal section of a filament, still lyinp: iu tlie tliick. 

 ji-elatinous nienibrane. The lowennost nueleus is couipletely divided; but tlie 

 central spindle niay still he dinily seeii. The luautle übers iu the latter cell 

 are more sharply detined. 



Fig. 35. Gloeocapsa. left aboiit two days iu chloroform water. Nothing 

 appears to remain in the dead. eolorless cells but the colorless cyanophyciu 

 graniiles. 



Fig. 30. Gloeocapsa, left 24 Imurs in chloroform water. Some of the 

 extracted phycocyanin may be seen in the spare between the cell and the 

 gelatinous wall. " The cells so treated are usually bright green; souietimes 

 3'ellowish. The grauulation is very distinct; obviously the grannles are 

 the sauie as those in tig. 35. 



Plate II. 



(Figs. 37—53, Calothrix tliermalh Hansgi rg.) 



Fig. 37. Section of the large end of a filament, in its gelatinous envelope, 

 showing the heterocyst with disorganized uuclens, and three vegeta- 

 tive cells, each with a nucleus in division. In the lowermost cell, 

 division is completed. In the other cells, the stain is not differentiated 

 siifficiently to show clearly chromosomes and central spindle. Mantle 

 fibers are dimly shown. The ring formed walls are not, in this in- 

 stance, well stained by the He id. 



Fig. 38. A preparation stained with Flem., showing dimly the central 

 body. The cavities in which the cyanophycin grannles lie are here 

 Seen to Surround completely the nuclear body. 



Fig. 39. Three cells near the attenuated end of the filament. The central 

 body, poorly stained with Flem., is here greatly elongated. 



Fig. 40. A similar section, stained with He id. Cavities containing cj^ano- 

 phj'cin are shown in the cytoplasm. 



Fig. 41. "'A broad, vegetative cell, stained with Heid. The achromati«-, as 

 well as the chromatic, strnctures are shown. 



Fig. 42. Gross section of a large vegetative cell in which chromatin gra- 

 nnles and linin appear somewhat fused together. Flem. 



Fig. 43. A cross section in which 16 chromatin grannles are seen. Heid. 



Fig. 44. A cross section, stained with Flem. At one side of the central 

 body is a slime globule. Many nnstained cyanophycin grannles are 

 shown in the cytoplasm. 



Fig. 45. A similar preparation to that in fig. 44. 



Fig. 46. A cross section of an elongated cell. Flem. 



Fig. 47. An elongated cell strongty stahied with Heid. 



Fig. 48. A preparation stained with Flem., in which only cyanophycin 

 grannles are stained red with safranin. 



Fig. 49. A heterocyst in longitudinal view, stained with Heid. The dark 

 body in the middle is probably a „Verschlußkcirper" (Kohl). 



Fig. 50. Gross section of a lietero(-yst, showing in the middle the „Vei-- 

 schlußkörper", and surronnding it what appears to be a nuclear 

 vacnole, bounded externally with a ring of disorganized chromatin. 



Fig. 51. A similar preparation, with central vacnole. 



Fig. 52. A 3^ouug heterocj^st in cross section; the gelatinous sheath is also 

 shown. 



Fig. 53. A young heterocyst in cross section; showing a dim achromatic 

 reticnlum in the nuclear cavity. 



(Figs. .54—60, Nostoc commune Vaucher.) 

 Fig. .54. A preparation stained with Heid. The central body not well 



differentiated. 

 Fig. 55. A similar preparation, showing about 8 chromatin grannles. Both 



slime globules and cyanophycin grannles are shown. 



