1909] STEVENS & HALL—VARIATION OF FUNGI 21 
To ascertain the variability in spore measurement under constant 
conditions and its variability as occasioned by changes in environ- 
ment, studies with several species of fungi were undertaken. 
The measurements were all made in water in which the spores 
had stood long enough to become fully turgid, taking only such spores 
as were completely ripe, as was shown by the fact that they were 
extruded from the pycnidium, ascus, or sporodochium naturally, 
without assistance. An eyepiece micrometer was used and the units 
here employed are usually one division of the eyepiece scale (equal 
to 3.7 #), which constituted in most cases as small a unit as could be 
used to advantage. Spore measurements involving half the division 
were recorded as with the next lower integer unless otherwise desig- 
nated. To avoid any possibility of unconscious selection, the spore 
lying closest to contact with the end of the micrometer scale at the 
completion of a measurement was taken for the next measurement. 
In the polygons each small square (one 256th of a square inch) 
represents one spore. 
We wish to acknowledge our indebtedness to Dr. G. H. Suutt, 
who has kindly read this portion of the manuscript, for calculating 
the constants, and to Mr. B. B. Hiccins, by whom most of the 
measurements were made and upon whose very accurate and pains- 
taking work the value of the measurements depends. 
AsScocHYTA CHRYSANTHEMI STEVENS 
A. Spores from the Secu SRE eeeeeee 
large pycnidium type (see p. 
18) 
i 
1 
te OE a BAB 
Pycnidium no. r. Alarge 
pycnidium produced in a 
colony which had_ very few 
pycnidia. : : 
aM tm 
ees 6 I 8 
M= 4.9645+0.0393 : 
T= 0.9787+0.0278 Fic. 16.— Ascochyta Chrysanthemi 
Ce 8 Stevens. Polygon of spores from pycnidium 
19.714 £0.551 | no. 1, large type. 3 should cover 20 squares 
n= 284 instead of 25. 
