128 
cynoglossi and P. echinospermi. Most of tlie oospores were measured 
in actual sections, which were obtained with a microtome, but I also 
give a number of measurements of P. echinospermi in optical section, 
since it is the usual method of measuring, and therefore gives results 
more strictly comparable with published measurements of other species. 
I am, however, convinced that the study of oospores in actual section 
offers great advantages over the common method of studying them in 
optical section. 
Table of measurements of ten oospores of Peronospora cynoglossi, Burrill, in actual sec¬ 
tion.* 
Diameter of 
oospore. 
Diameter 
of oospores 
lacking 
epispore. 
Thickness 
of endo- 
spore. 
Thickness 
of epi¬ 
spore. 
Diameter of 
oogonium. 
27 by 25 
18 
If 
2 -4 
30 by 28 
27 by 26 
21 
1| 
2 -4 
32 by 30 
30 by 26 
24 
2 
2 -3 
44 by 31 
30 by 28 
22 
2 
1 -3 
32 by 29 
30 by 28 
24 
2 
2 -4 
36 by 32 
30 by 29 
24 
2 
2 -4 
36 by 30 
32 by 30 
27 
2 
1H 
44 by 32 
33 by 31 
26 
3 
IH* 
38 by 32 
34 by 31 
27 
2 
2 -3 
40 by 34 
40 by 33 
28 
' 2 
2*-5 
40 by 35 
* These oospores were measured from a specimen on Cynoglossum.Tirginicum , (A. B. Seymour, Illinois 
State Laboratory of Natural History. No. 4703, May 16, 1882. Sanburn, Ill.) They were measured in 
actual section in water, as indicated in the other tabulations of measurements given. One division of 
the eye-piece micrometer equalled 2 g. All measurements given in ft’s. I am indebted to Mr. Waite 
for this specimen, as well as for the permission to use his whole herbarium for comparisons. 
Table of measurements of twenty-five oospores of Peronospora echinospermi, Swingle, in 
optical section, t 
Diameter 
of 
oospore. 
Diameter 
of oospore 
without epi¬ 
spore. 
Thickness 
of endo- 
spore. 
Thickness 
of epi¬ 
spore. 
Diameter 
of 
oogonium. 
*38 by 36 
31 
2 
3i to 6 
54 by 44 
39 by 37* 
30 
1* 
3| to 6 
54 by 45 
40 by 39 
29 
2 
2 to 6 
60 by 46 
*40 by 39 
33 
2* 
3 to 5 
58 by 50 
40i by 39 
31i 
It 
4* to 7* 
54 by 54 
42 by 40* 
31i 
11 
3 to 6 
55* by 54 
42 by 40* 
32* 
11 
4* to 7* 
63 by 61 
*42 by 41 
32 
11 
4 to 6 
76 by 50 
43i by 37i 
31* 
2* 
4J to 9 
61* by 48 
43i by 39 
30 
2* 
6 to 7* 
67* by 48 
43i by 40* 
30 
lb 
4* to 9 
63 by 42 
43i by 42 
30J 
11 
4* to 6| 
63 by 61* 
45 by 42 
32 
It 
4 to 7* 
66 by 54 
45 by 42 
36 
11 
6 to 9 
69 by 55* 
45 by 44 
33 
21 
4 to 6 
54 by 52 
*45 by 44 
34 
2* 
4 to 5 
60 by 56 
*46 by 41 
32 
3 
4 to 5 
56 by 50 
46 by 44 
33 
2 
4 to 6 
56 by 52 
*46 by 46 
35 
21 
4 
72 by 50 
4«* by 45 
35* 
2*' 
4* to 7* 
61* by 52* 
48 by 48 
38 
21 
4 to 5 
72 by 54 
*50 by 48 
40 
21 
3 to 5 
78 by 60 
51 by 40* 
30 
11 
4* to 9 
57 by 48 
51 by 45 
36 
11 
6 toll* 
63 by 54 
57 by 45 
35* 
2* 
6 to 13* 
69 by 60 
1 These specimens were measured from oospores teased out of the tissues from the same specimens 
and in the same manner as indicated in the following table of measurements. One division of the eye¬ 
piece micrometer equaled 2 g. All were from Echinospermum liedowskii Lalun, var. occidentale Wats, 
except those marked with an asterisk (*)> which were from E. liedowskii Lehm, var. cupulatum. Gr. 
All measurements in ft’s. 
