Apr. 26, 1924 
L eather Rot of Strawberries 
361 
Table I. —Summary of measurements of conidia 
Class (in microns) 
Number of conidia 
in each class ac¬ 
cording to— 
Class (in microns) 
Number of conidia 
in each class ac¬ 
cording to— 
Length 
Width 
Length 
Width 
16-17.. 
3 
38-39 
26 
1 
18-19... 
2 
5 
40-41 . 
18 
20-21.. 
2 
23 
42-43 . 
1 
22-23... 
9 
86 
44-45.. 
6 
24-25.. 
28 
119 
46-47 . ... 
2 
26-27... 
32 
93 
48-49... . 
1 
28-29 
45 
49 
30-31... 
67 
18 
Total 
400 
400 
32-33.. 
64 
1 
Mean _ 
32.26 
25.09 
34-35.. 
50 
1 
Mode. _ . , _ 
30.31 
24.25 
36-37.. 
37 
1 
Table II .—Arrangement in classes of the ratios of the length to the width of conidia t 
showing the limits of variation 
Class (in microns) 
Number of 
conidia in 
each class 
Class (in microns) 
Number of 
conidia in 
each class 
1.00-1.04. 
12 
1.50-1.54 . . 
16 
1.05-1.09... 
22 
1.55-1.59... 
6 
1.10-1.14. 
34 
1.60-1.64 .. 
5 
1.15-1.19... 
56 
1.65-1.69. 
4 
1.20-1.24____ 
63 
1.70-1.74..•.. 
2 
1.25-1.29 
52 
1.30-1.34..... 
44 
Total.. 
400 
1.35-1.39.... 
25 
Mean...... 
1.24 
1.40-1.44... 
36 
Mode_ 
1.20-1.24 
1.45-1.49.... 
23 
Conidia from the Louisiana material discharged zoospores within five minutes 
after mounting in water on a slide, while those from Arkansas material failed to 
produce zoospores at any time even after repeated trials. Material from both 
sources were examined within an hour after collection. 
Both in culture and on berries collected in the field the conidia were found 
germinating in the direct manner, either by a simple germ tube or by the forma¬ 
tion of secondary and even tertiary conidia (PI, 2, C to G). In mounts 
from a few cultures these secondary and tertiary conidia were found discharging 
zoospores. 
The manner of zoospore discharge, for all classes of conidia, is the same as 
that already described (S, 9) for P. cactorum and other Phytophthora species; 
that is, there is first a bulging of the papilla and a movement outward of the 
already differentiated zoospores. The first three or four move out so quickly 
that they seem almost to burst out, though they go singly through the narrow 
passage or neck at the tip of the conidium. All of them assume an hour-glass 
shape as they pass through the neck. The first few that come out are held 
together for a few seconds by the vesicle formed by the bulging out of the papilla 
but finally separate—presumably when the vesicle breaks, though the actual 
breaking was not seen—remain quiescent for a few seconds more and then swim 
rapidly away. The zoospores that follow the first lot come out more slowly, 
although the total time for what might be called normal discharge is about 
thirty seconds. In fact, it is almost certain that if the zoospores do not all 
come out within that time some of them will not come out at all. Those that 
remain within the conidium frequently germinate there, the germ tubes growing 
out through the conidium wall. 
