A case of changed polarity in Spirogyra elongata 
F. L. PIcKEItT 
(WITH PLATE 36) 
On June 19, last, the writer was examining some filaments of 
Spirogyra elongata (Berk.) Kg., taken from a ditch running through 
Indiana University campus, and found the holdfast structure 
shown in PLATE 36, FIG. 1. This structure seemed to be growing 
rapidly, as a camera-lucida drawing was quickly made. Three 
hours later a second sketch was made (FIG. 2), showing consider- 
able development. | 
The slide was carefully kept in a light moist chamber for ten 
days. The water on the slide harbored a number of animal- 
cules,—rotifers, phacus, ameba, etc.—which with the algae seemed 
to keep up a life balance. Rapid growth and division of cells 
in the filaments, as well as the many bubbles of oxygen produced 
when the light was strong, showed that conditions were quite 
favorable for algal growth, Most of the filaments were held in 
More or less sharp curves by the cover glass, but some were quite 
Straight and free from stress (FIG. 7 and 8). The cells of Clado- 
phora were old and well covered with diatoms and particles of flint. 
The slide was frequently examined and several branchlike 
structures were found. The first one found remained as shown 
FIG, 2, but another was seen in process of development (FIG. 3 
and 4). In every case where attachment had occurred, the 
Spirogyra was fastened to a thread of Cladophora. 
The structures shown in FIG. I-6 are outgrowths near the end 
of a filament, near a dead cell or at a point of physical stress, and 
are probably holdfasts. In such cases the change in polarity 
Own is probably due to the abnormal stress, as suggested by 
Plefler (Pfeffer-Ewart 2: 1 59. 1900). A structure similar to 
these was found in a chance examination of S. communis by Prof. 
P.M. Andrews in November 1904. His hitherto unpublished 
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