420 BOTANICAL GAZETTE [DECEMBER 
When young specimens of A. phalloides, which have longer stipes 
and respond more quickly, were used, the tip of the stipe was carried 
beyond the vertical 2° to 20°, then it stopped and moved back toward 
and beyond the vertical 1° to 6° on the other side, and by a repetition 
of this process finally came to rest in the vertical position. ig. 7 
shows a series of drawings of one specimen of A. phalloides in which 
the supra-curvature was neutralized. Fig. 3 shows this toadstool 
just before it came to its final vertical position. This fluctuation 
only takes place if the plant is still growing when the induced response 
ceases. 
In an attempt to locate exactly the perceptive zone, all the pileus 
except that part directly above and which forms a continuation of the 
stipe was removed in the manner shown in fig. 8. These plants were 
then allowed to develop in the dark in a horizontal position for 24 
hours, and the result is shown in fig. 8. The stipe itself bent, but 
there was no curvature in that part which belonged to the pileus. 
This shows that the responsive zone is not situated within the pileus. 
The entire pileus was then carefully removed from the tip of the 
stipe in many plants by a transverse cut where the gills join the stipe. 
Each specimen was then placed in a horizontal position in the dark 
and allowed to remain 24 hours. The geotropic response here was 
normal (fig. 9). The stipe, which was bent downward at first, began 
to bend upward slowly, then more rapidly, carrying the tip beyond 
the vertical. This shows that the responsive zone is situated within 
the stipe. 
A further attempt to locate the responsive zone was made. Glass 
tubes were cut in pieces of different lengths and these were placed 
over the bases of the stipes of plants from which the pileus had been 
removed. This left 1-4™™ of the upper end of the stipe exposed 
beyond the end of the tube. These tubes were held firmly in a 
horizontal position by wire, and the plants were kept in the dark for 
24 hours. In every case where elongation had not ceased, there 
was a decided upward curvature of the stipe beginning at the end of 
the glass tube (fig. 10). In this case the stipe was 8™™ long, 2"™ of 
this projecting beyond the end of the tube when the experiment was 
set up. After twenty-four hours the stipe projected 217” beyond 
the tube. It had curved upward at the end of the tube, making an 
