DAMPING-OFF IN FOREST NURSERIES. 
67 
thick-walled truncate-tipped hyphae and characteristic branching. A 
further difficulty in the direct-examination method, unless the seed- 
lings are sectioned, is in distinguishing between Corticium hyphae 
which are in the tissues and those outside. The well-known habit 
of the Corticium of sending hyphae superficially over the surface of 
plants which it is not appreciably injuring makes it evident that only 
hyphae actually found in the tissues have diagnostic value. Direct 
microscopic examination is, furthermore, very likely to fail to detect 
Fusarium. The planted-plate method therefore appears the better of 
the two, and the results of the culture diagnoses appearing in the 
lowest two lines of Table IX deserve probably more attention than 
the total occurring a few lines above, in which the results of direct 
examination of the seedlings are also included. The high proportion 
of Corticium reported from the Michigan and Minnesota nurseries 
is probably due in part to the fact that most of the examinations 
made there were of the direct microscopic type. 
Table IK.— Results of the examination of damping -off foci in coniferous seed 
beds for Pythium dclaryanum, Corticium vagum, and Fusarium spp. 
Untreated beds. 
Beds of heated 
soil. 
Beds treated with 
strong acids. 
Grouping. 
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By locality: 
Berkeley, Calif 
4 
22 
34 
18 
20 
224 
42 
4 
45 
13 
12 
3 

6 
4 
4 
124 
15 

14 
11 
3 
1 
19 
20 

9 
45 
21 
4 
33 
7 
3 
2 

13 
7 
155 
5 
1 
2 
1 
9 
5 
5 

2 
Garden City, Kans.— 
Garden City Nurseries 
14 
15 
28 
5 
2 
10 



7 
6 
17 
28 
16 
99 
1 
8 
9 
34 

2 
2 
2 

q 
Kansas Nurseries (sand) 
8 
61 
n 
East Tawas, Mich. — 
1 
13 
1 
7 

6 
n 
2 
7 
2 

3 
Total: 
Number 
438 
100 
184 
42 
162 
37 
204 
47 
64 
100 
19 
30 


33 
52 
163 
100 
64 
39 
12 
5 
8? 
50 
By -diagnostic methods: 
Direct examination — 
Nnmber 
156 
100 
282 
100 
39 
25 
145 
51 
108 
69 
54 
19 
25 
16 
179 
63 

16 
100 
147 
100 
6 
38 
58 
39 
8 
50 
4 
3 
4 
?,5 
Planted-plate cultures — 
64 
100 
19 
30 

33 
78 
Percentage 
52 
53 
