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-know r n habit 

 of the Corticium of sending hyphse superficially over the surface of 

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

 hypha? 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 

 for I'ythiuin debdryanwn, ('ort-k'iutn vayum, and Fusarium spp. 



