428 BOTANICAL GAZETTE [NOVEMBER 
the chromatophore correctly. She has figured it incidentally as 
it appears to the casual observer. 
Material and methods 
My observations were made on several species of Zygnema. The 
material came from the vicinity of Chicago and from Dr. TRAN- 
SEAU’S laboratory. It was killed in 1 per cent chromoacetic acid, 
part of it at 11:00 P.M. to secure cells which were dividing, and part 
of it at 11:00 A.M. to catch the cells in an active vegetative condition. 
Filaments were mounted whole in Venetian turpentine and 
stained with anilin blue and Magdala red and with gentian-violet 
and anilin blue in order to differentiate the parts of the chromato- 
phore. Iron hematoxylin was also used for some preparations. 
Most of my observations were made on the whole filaments. Many 
of the drawings are optical sections of whole chromatophores. 
The advantage in this method lies in the fact that the true sizes 
and relations of the starch grains and the exact extent of -the 
pyrenoid in the chromatophore can be ascertained by focusing up 
and down. The use of sectioned material exclusively might lead 
to errors of interpretation by taking the transverse section of a 
grain for a small one, or by failure to see the full extent of the 
pyrenoids. Longitudinal and cross-sections of cells 3 u thick were 
also made and were stained with gentian-violet and safranin, iron 
hematoxylin, and Flemming’s triple stain. An 8X ocular and a 
2mm. objective were used for examining the preparations. 
I wish to thank Dr. C. J. CHAMBERLAIN for much valuable help 
and for his many suggestions. 
Description 
The chromatophores lie, one on each side of the nucleus, in the 
middle of the cell, suspended there by means of bands of cyto- 
plasm which radiate from them to the layer of the cytoplasm along 
the cell wall (fig. 1). Under low-power lenses these bands appear 
to be part of the chromatophore and have led writers of textbooks 
to speak of the star-shaped chromatophore of Zygnema. The 
chromatophore is really round or oval in shape. It is a plastid 
containing imbedded in its substance a pyrenoid, which lies near 
