350 BOTANICAL GAZETTE [NOVEMBER 
openings, and those apparently indifferent. After an examination of the entire 
preparation in each case, those holes were selected for the counts which repre- 
sented the average condition. In calculating the percentages from the counts 
the difference between those attracted and those repelled was made the divi- 
dend, and the'total number within the observed area was made the divisor. 
This method is open to at least 3 objections. In the first place, 
no definite method is given for distinguishing between the 3 classes 
of hyphae, that is, between the indifferent hyphae on the one hand, 
and those turning away from or toward the openings on the other 
hand. Without some such definite rule as that used in the method 
employed in the present paper, the matter of deciding their direc- 
tions is likely to be influenced to a large degree by the personal 
equation, on account of the great variety of curves and angles | 
which the hyphae assume. In the second place, apparently ail the 
hyphae found in the area at the time of examination were included. 
It is clear that by such a method one must include some of the 
hyphae coming from spores located outside the special area; and 
if we are right in concluding that Futron’s classification of direc- 
tions is similar to ours, it is evident that in this way a portion at 
least of the A class hyphae belonging to an outer zone would be 
counted, whereas the B and D classes would be mostly, and the 
C class hyphae of that zone would be entirely, neglected. Thus, 
even if there were no turning toward the holes at all, and the number 
of the A class in the prescribed zone were only the normal 25 per 
cent, by counting in some of the A class from the zone outside, the 
resulting figures would inevitably, though falsely, indicate the 
existence of a chemotropic reaction. Moreover, this error would be 
greater as the amount of real turning increased, and it would also 
increase with the growth in length of the hyphae, since eventually 
some of those from zones still more remote would reach into the 
prescribed zone. In the third place, although the area in the plane 
of the hole was clearly defined by Futron, no statement was made 
as to the hyphae found in the parallel planes above the hole. If 
these were estimated in the same way as those in the plane of the 
hole, Futton was really considering the hyphae in a cylinder of 
medium standing over the hole and reaching to the free surface of 
the film. If this were the case, he must have counted in hyphae 
