124 



MISSOURI BOTANICAL GARDEN. 



!- 



to those recorded for Erysiphe graminis by Salmon.* 



iust mentions this fungus especially as being one 

 which is largely dependent upon the state of development 

 of the host, citing the case where it attacks the host plant 



o 



Alb 



h 



were in a condition particularly susceptible to the attack of 

 the Peronospora, a condition which has not reappeared 

 since that time. 



EXPLANATION OF PLATES. 



Plate 22. — Upper surface of leaf of cauliflower, showing the charac- 

 teristic spots due to the growth of Per onospor a parasitica, natural size. 



Plate 23. — Lower surface of leaf, showing the tufts of the fungus, 

 natural size. 



Plate 24. — Lower surface of leaf in a more advanced stage of the dis- 

 ease, natural size. 



* Salmon, Ernest S., Cultural experiments with biologic forms of the 



Ervsiphaceae. 



1904) 



t Magnus, P., Das Auftreten der Peronospora parasitica, be einflusst 

 von der Beschaffenheit und dem Entwickelungszustande der Wirtspflanze. 

 (Berichte d. d. bot. Ges. 12. Generalversammlungsheft. pg. 39. 1894). 





