GROWTH OF ENDOTHIA PARASITICA 
117 
throughout their length. These two curves are in turn very similar 
to the curve of growth, although they rise somewhat more rapidly 
in the more southern localities. This is in general the same relation 
which was found to hold for the years ending in May and in August, 
1 91 5, at a still larger number of localities. Taken together these 
results furnish a considerable body of evidence that either of these 
methods of calculation expresses satisfactorily the relation between 
air temperature and the growth of Eiidothia parasitica within this area. 
In computing the physiological temperature efficiency the daily 
mean temperatures were calculated by the formula mean = 3^ 
(maximum + minimum). For this mean temperature the equivalent 
index from Livingston's (3) Table II, p. 406, was substituted and the 
sums of these daily indices considered the index for the year. 
Table IV 
Lateral Growth of Cankers of Endothia parasitica and Temperatures Computed in 
Various Ways for the Year Ending in May, IQ16 
Growth 
in Centi- 
meters. 
Percent 
Remain- 
der 
Sum- 
mation 
Indices 
Percent 
Expo- 
nential 
Sum- 
mation 
Indices 
Percent 
Physio- 
logical 
Sum- 
mation 
Indices 
Percent 
Concord, N. H 
14 
100 
2,967 
100 
366 
100 
5,514 
100 
15 
107. 1 
3,038 
102.4 
373 
IOI.9 
5,576 
lOI.I 
Amherst, Mass 
17 
121. 4 
3,380 
II3.9 
431 
II7.8 
6,673 
121. 0 
Woodstock, N. Y 
15 
107. 1 
3,100 
104.6 
386 
105.5 
5,632 
102.2 
Washington, D. C 
21 
150.0 
4,976 
167.7 
603 
165 
11,080 
201. 1 
Charlottesville, Va 
23 
164.3 
5,366 
180.7 
636 
174 
11,620 
211 
The results are given in Table IV. It will be observed that the 
physiological temperature indices rise considerably faster from north 
southward than do the summation indices, and that accordingly 
they correspond rather less well with the rate of growth of the fungus. 
It is of course not surprising that the results obtained from the 
use of the physiological temperature indices given by Livingston should 
not more nearly approximate the growth of Endothia parasitica, since, 
as Livingston correctly points out (p. 407), the indices are based upon 
tests of only a single plant species, maize, and from the growth of 
seedlings, and it is entirely probable that they are not even approxi- 
mately true for plants of some other species. On the other hand, 
when the necessarily approximate nature of many of the data are 
considered, the agreement between the curve of growth of cankers of 
