222 AGRICULTURAL EXPERIMENT STATION, [elan. 



the Botrijtis. I have preserved the l)lock of potato with 

 Botrytis threads and sclerotia as evidence of the correct- 

 ness of these statements. It is, I believe, quite within 

 bounds to say that the results described raise a very strong 

 presumption in favor of the view that Sclerotinia Libertiana 

 possesses a conidia] stage of the Botrytis type. This view 

 is further strengthened by the observations to the same effect 

 made in the study of a disease of rape l)y Frank,* although 

 he identified his Botrytis as one w^hich is known to be con- 

 nected with another species of Sderoihna. 



As to the identity of the Botrytis in question, the indefi- 

 niteness of the descriptions of the various so-called species, 

 and the undoubted multiplication of specific names beyond 

 all reason, render it difficult to speak with certainty. But 

 the form on the cucumber appears to me to be identical in 

 all respects with that previously described f as the cause of 

 the rotting of lettuce in the greenhouse, and believed to be 

 the form known as Botrytis vulgaris Fries. Some points 

 of its structure are poorly shown in fig. 13. Unfortunately, 

 I was not able to make infection experiments when livino- 

 spore material was available ; but, in view of Kissling's 

 results I with a closely related Botrytis, it seems probal)Ie 

 that the conditions which govern its attacks as a parasite are 

 similar to those above described for the ascosporic form. 



Consideration of the life history above sketched shows 

 clearly that the key to the situation, so far as the control of 

 this disease is concerned, is to be found in the destruction 

 of the sclerotia. If plants which shoAV the disease be 

 promptly removed and destroyed, and the development of 

 sclerotia be thus prevented, while careful watch is kept for 

 any sclerotia accidentally allowed to form, one need have little 

 fear of serious loss in future crops, even on the same soil. 

 It is only whore diseased plants are neglected, and sclerotia 

 are allowed to develop and fall to the ground to serve as 

 sources of infection for the next crop, that serious attacks 

 can continue from season to season. The control of this 

 disease does not require (;ven the trouble of spraying, but 



* Die Krankheiten der Pflanzen, p. 530: 1880. 



t Niiitli Report Massachusetts Experiment Station, p. 219. 



+ Iledwigia, 1889, p. 227. 



