Feb. i2, 1917 
Studies of the Genus Phytophthora 
269 
Table; VII .—Summary of differences in the means of the conidia of species of 
Phytophthora 
Species. 
Difference in means. 
Difference in means 
divided by prob¬ 
able error of dif¬ 
ference. 
Length. 
Width. 
Length. 
Width. 
fs 
t* 
P. nicotianae and P. jatrophae . 
I2.07±0. 427 
7. 6o±o*36i 
28.27 
21.05 
P. parasitica and P. arecae . 
4. 28± .425 
6. 66± .237 
10.07 
28.10 
P . fagi and P. cactorum (Phyllocactus sp.)... 
4 -° 4 ± -314 
• 05 ± .188 
12.87 
. 26 
P. infestans and P. erythroseptica . 
X 7 - 77 ± -336 
9-38± *204 
52.89 
45-98 
P. infestans and P. phaseoli . 
P. cactorum (Panax sp.) and P. cactorum (Phyllocactus 
• 79 ± -243 
. 78± . 146 
3-25 
5-34 
l.o7± .295 
. 34± . 162 
3-63 
2.10 
P. parasitica and P. erythroseptica . 
l.2i± .407 
4. 26± .230 
2.97 
18. 52 
P. arecae and P. erythroseptica . 
3 -° 7 ± .446 
2-40± .257 
6.88 
9-34 
P. syringae and P. cactorum (Phyllocactus sp.). 
2. 17 ± .441 
• 39 ± -194 
4.92 
2.01 
The probable errors in the differences of the statistical results are 
shown in Tables VII and VIII. Examination of these tables shows that 
the differences in length of conidia of P. nicotianae and P. jatrophae f 
P. parasitica and P. arecae , P. fagi and P. cactorum , and P. infestans and 
P. erythroseptica are, without doubt, significant. On the other hand, the 
figures confirm the previous observation and statement that the pairs 
P. infestans and P. phaseoli, P. cactorum from Panax sp. and P. cactorum 
from Phyllocactus sp., P. parasitica and P. erythroseptica can not be 
distinguished by their differences in length. 
Table VIII .—Summary of differences in the mean diameter of oospores and chlamydospores 
of species of Phytophthora 
OOSPORES 
Form. 
Difference in 
mean diameter. 
Difference 
in mean 
diameter 
divided by 
probable 
error of 
difference. 
Arecae and erythroseptica . 
3 - 35 ±°- 19 8 
• 59 ± • “7 
6. &7± . 176 
3. 44 i • 149 
2. 72± . 135 
16. 92 
5. 04 
38. 9 2 
23. 09 
20. 15 
Cactorum {Panax sp.) and cactorum {Phyllocactus sp.). 
Phaseoli and arecae . 
Fagi and cactorum {Phyllocactus sp.). 
Syringae and cactorum {Phyllocactus sp.). 
CHLAMYDOSPORES 
Nicotianae and jatrophae 
Jatrophae and faberi . 
Faberi and parasitica .... 
4* 05± .272 
6. 09 ± . 246 
7- 83 ± • 209 
14. 89 
24. 76 
37-46 
