290 
Journal oj Agricultural Research 
Vol. XXX, No. 5 
tioned above, where the figures fall on 
the wrong side for two criteria. On 
account of the greater irregularity in 
the ratio figures, a variation above or 
below the line is of less importance 
than a similar variation in length or 
wall thickness mean. If the two latter 
criteria only are considered there are 
but 2 means out of 40 which are defi¬ 
nitely out of line—the length means 
for C . occidentale in sets 5 and 17— 
which makes the biometric diagnosis 
correct in 95 per cent of the trails. 
The relation of the means of sets 1 to 
20 to the diagnostic division points 
for the length mean and for the ratio 
of mean length divided by mean width 
is shown again in Figure 4, a type of 
figure which appears to be particularly 
satisfactory for illustrating the appli¬ 
cation of the criteria of size and shape 
to biometric diagnosis. Each of the 
plotted points represents both the 
mean length and mean width of 100 
measurements. The means for C. ribi- 
cola are shown as dots and the means 
for C. occidentale are shown as circles. 
Set numbers have been omitted pur¬ 
posely, but the position of the means 
for any set can be found by reference 
to the mean values given in Tables 
I to III. For example, the means for 
set 1 are indicated f>y the dot and 
circle at 22.7 and 14.6, and at 24.2 
and 15.4, respectively. 
The diagnostic division point for 
the length mean, represented by the 
horizontal line drawn at 24.1 in Figure 
1, is here represented as a vertical 
line at 24.1. The diagonal line, drawn 
cc 
to satisfy the equation t/=repre¬ 
sents the diagnostic division point for 
mean length divided by mean width. 
The figure illustrates clearly the a scat¬ 
ter’’ or shotgun pattern of the mean 
sizes for each of the 100’s measured, 
the fact that length is the factor 
governing the distribution of the 
points to the left or right of the 24.1 
line, and the effect of variation in size 
on the position of the plotted points 
with respect to the diagonal. 
The difference between the 1,000 
spore length means of the two species 
(see Table Y) for the Field series is 
1.76 ±0.092, for the Block Island series 
1.82 ±0.072, and for the Greenhouse 
series 0.81 ±0.099. No attempt will 
be made at present to establish the 
significance of these differences with 
respect to their probable errors, since 
it seems preferable to leave any such 
discussion as well as a more detailed 
description of the mounting measuring 
and analysis methods to a later paper. 
The ranges for the spore sizes of the 
two species are given in Table VI. It 
is obviously impossible to separate the 
species on the basis of the range of the 
spore sizes. Ranges obtained by sub¬ 
tracting and adding the standard 
deviation to the mean for each dimen¬ 
sion—which might be called “ standard 
ranges”—are, however, more signifi¬ 
cant. These ranges in the three 
series are given in Table VII. In 
spite of the fact that the standard 
ranges are much more accurate in¬ 
dices of the spore sizes than the com¬ 
plete ranges, they do not serve to 
bring out the differences between the 
species as clearly as the tabular or 
graphic representation of the means. 
It must be admitted after exami¬ 
nation of the graphs in Figures 1 and 2 
that C. ribicola and not C. occidentale is 
the species which appears to be “ ab¬ 
normal” under greenhouse conditions. 
No adequate explanation of the “ ab¬ 
normality” is possible at present. 
In the Field series the measurements 
of 5 lots of 20 spores each were grouped 
together, as has been previously stated. 
Table VI.— Ranges for length and width of the urediniospores of Cronartium ribi¬ 
cola and Cronartium occidentale 
Series 
C. ribicola 
C. occidentale 
Length 
Width 
Length 
Width 
Field........ .. 
16-34 
10-22 
16-37 
10-21 
Block Island... _ . 
13-32 
10-21 
18-37 
10-22 
Greenhouse.... .. _ 
15-40 
10-24 
16-39 
10-23 
Table VII.— Standard ranges for the length and width of urediniospores of Cronar¬ 
tium ribicola and Cronartium occidentale 
Series 
C. ribicola 
C. occidentale 
Length 
Width 
Length 
Width 
Field... 
20.9-26.1 
13.2-16.8 
21.7-28.7 
13. 5-17.1 
Block Island........ 
20.5-25.7 
13. 5-16. 7 
22. 0-27.8 
13. 2-16.6 
Greenhouse....... 
20. 7-27. 5 
13.4-17.4 
21. 6-28.4 
13. 5-17.3 
