364 
Vol. XXVIII, No. 4 
Journal of Agricultural Research 
Table III .—Summary of measurements of oospores 
Class (in microns) 
Number of! 
spores in | 
each class ! 
Class (in microns) 
Number of 
spores in 
each class 
14 ... 
2 
27...... 
63 
15. .. ..... 
2 
28...... 
58 
16... 
1 
29__..... 
41 
17 . 
- 
30..... 
36 
18 . .. .. . 
3 
31..... 
11 
19 . . _ _. 
7 
32...... 
13 
20 .... .. 
10 
33.... 
3 
21 . 
14 
34—..... 
6 
22 ... 
14 
19 
35...... 
3 
23 
24 ....... 
16 
Total _ 
400 
25 ...... 
34 
Mean_ 
‘ 26.42 
26 . ..... ..... 
38 
Mode__—.. 
27.0 
The above description and measurements are believed to establish it as a fact 
that the organism dealt with in this paper is Phytophthora cactorum, since they 
agree so closely with those already published for that fungus by other workers 
(1, 8, 10). The finding of both paragynous and amphigynous antheridia in cul¬ 
tures of the strawberry Phytophthora is still further evidence that the organism 
is P. cactorum since Lafferty and Pethybridge ( 3) have reported the discovery 
of both kinds of antheridia in cultures of P. cactorum obtained by them from 
various sources. N 
INOCULATION EXPERIMENTS 
Two methods of inoculation were used, one of them in the laboratory at the 
University of Chicago, the other in the field laboratory at Beebe, Ark. Procedure 
in the former was as follows: 
Berries apparently free from disease were selected either from quart boxes 
purchased on the market (out of crates stamped “Klondike,” “Haverland” or 
“Dunlap”) or were picked from a small patch of Progressive, an everbearing 
variety, to which the writer had access. These berries were washed three or four 
times with sterile water, placed in sterile glass moist chambers in lots of 20 to 25 
and inoculated by forcing a small fragment of mycelial growth from a pure 
culture down into the flesh. They were then covered up, but in such a way as to 
allow some ventilation, since it was found that too close covering kept the 
berries so moist that Botrytis on northern-grown berries and Rhizopus on 
berries from all sections frequently caused excessive decay before Phytophthora 
got well started. 
Within three days, at 20 to 25° C., berries inoculated by this method, if they 
had escaped Rhizopus (or Botrytis), showed vascular browning and slight 
softening; within four days they showed a marked browning of the surface and 
had reached the tough leathery condition described earlier in this paper. For 
some unknown reason they did not have quite the appearance of berries naturally 
infected in the field, though they always gave Phytophthora when plantings were 
made from them, under aseptic conditions, into agar tubes. They were atypical 
externally, in that they did not show the color pattern or color transition, from 
pale yellow to brown to purple to red. 
The same is true of berries inoculated by the second method, which, never¬ 
theless, gave practically 100 per cent infection by Phytophthora. These berries 
(varieties Klondike and Aroma) selected as before as free or apparently free of 
disease, were washed with sterile water as soon as they were brought in from the 
field; 20 to 25 of them were then placed on clean, but not sterilized, newspaper, 
in about a quarter of an inch of water in pans, with five or six moldy “water- 
soaked” (leather rot) berries scattered among them. The experiment was al- 
