DAMPING-OFF IN FOREST NURSERIES. 



67 



thick- walled truncate-tipped hyphse and characteristic branching. A 

 further difficulty in the direct-examination method, unless the seed- 

 lings are sectioned, is in distinguishing between Corticium hyphse 

 which are in the tissues and those outside. The well-known habit 

 of the Corticium of sending hyphse superficially over the surface of 

 plants which it is not appreciably injuring makes it evident that only 

 hyphse 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 IX. — Results of the examination of damping-off foci in coniferous seed 

 beds for Pythium dcbaryanum, Corticium vagum, and Fusarium spp. 





Untreated beds. 



Beds of heated 

 soil. 



Beds treated with 

 strong acids. 



Grouping. 



a 



a 



(3 

 M 



'o 



o 



Ph 



Number 

 showing — 



•6 



35 



.a 

 a 



03 



M 



<D 



'a 



o 

 Ph 



Number 

 showing — 



tjj 



a 



03 

 M 



'3 

 o 



Ph 



Number 

 showing — 





a 



g 



3 



Ph 



a 



3 

 jo 



o 

 O 



03 



s 



Ph 



a 



g 

 3 



Ph 



a 



'o 



M 



o 

 O 





a' 



s 

 3 



PH 



a 

 .g 



-+^ 



fH 



o 

 O 



a 

 .g 



03 



B 



Ph 



By locality: 



4 

 22 



34 



18 



20 



224 



42 



4 



45 

 13 

 12 



438 

 100 



156 

 100 



282 

 100 



3 

 

 6 



4 

 4 

 124 

 15 

 



14 

 11 

 3 



1 



19 

 20 







9 



45 



21 



4 



33 

 7 

 3 



162 



37 



108 



69 



54 

 19 



2 

 

 13 



9 

 7 

 155 

 5 

 1 



2 

 1 



9 



204 



47 











5 



5 







2 

































Garden City, Kans. — 



14 

 15 



28 



5 

 2 

 10 





 

 



7 

 6 

 17 



28 



16 



99 



1 



8 



9 



34 







2 

 2 

 2 







q 





8 





61 





















East Tawas, Mich. — 











1 

 13 



1 



7 





 6 



n 













t 





7 



64 

 100 







2 



19 

 30 









 



3 



33 

 52 









64 

 39 



6 

 38 



58 

 39 



12 

 5 



8 

 50 



4 

 3 





Total: 



184 

 42 



39 

 25 



145 

 51 



163 

 100 



16 

 100 



147 

 100 



8? 





50 







By diagnostic methods: 

 Direct examination — 



25 

 16 



179 

 63. 



4 











?,5 



.. Planted-plate cultures — 



64 

 100 



19 

 30 





 



33 

 52 



78 





53 



