284 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9. 
Figures i and 2 are of examples taken from the material collected in 
June. This material shows a much greater uniformity in the arrangement 
of the chromatophores, most of them being par- 
allel irrespective of their location in conjugating 
filaments. Figure 3 is of a conjugating form from 
the material collected in November, 1920. In this 
by no means exceptional case, the chromatophores 
in the course of a few cells may be seen to change 
from regular to loose spirals, and finally to straight 
and discontinuous bands as the vegetative cells 
approximate in position the fertile cells of the 
filaments. Such successive relaxation in the bands 
is worthy of further investigation, for in this be- 
havior may be found a clue to the understanding 
of some of the physiological changes that the cells 
undergo in their transition from the vegetative to 
the reproductive state. 
The following is a description of this new form 
which may be appropriately designated as S. recti- 
spira. 
Spirogyra rectispira. Diameter of vegetative 
filaments 150-160^1, cells 3^ to 2 times longer than 
diameter, chromatophores 6-1 1; chromatophores 
straight or somewhat sinuous, sparingly branched 
or discontinuous ; in some filaments, particularly 
when not conjugating, all gradations to be seen 
from straight chromatophores in cells adjoining 
conjugating cells to spirals making to i turn in 
the cell. Fertile cells not or only slightly inflated, 
zygospores 140-108^1, orbicular or subglobose, not 
completely filling the cells. 
This species ranks with S. crassa in the diam- 
eter of its filaments as the largest of the genus. It 
is distinguished from 6*. crassa by its much smaller 
zygospores and by the parallel arrangement of the 
chromatophores in vegetative cells of conjugating 
threads. The pyrenoids with their starch accre- 
tions are at all times much smaller than those of S. 
crassa, and the chromatophores are much narrower. 
At the beginning of conjugation all the bodies 
making up the cell contents become greatly increased in size, filling the 
cells, the latter before the blending of the chromatophores of the two 
sexual cells being a brilliant green in contrast to the paucity of chlorophyll 
in the adjoining vegetative cells. 
Hunter College, 
New York City 
Fig. 3. S. rectispira 
collected in November, 
1920, showing changes in 
position of chromato- 
phores in cells in a linear 
series. 
