354 Report of the Mycologist of the 



growth — spores may be found attached to the sporophores and in 

 all stages of growth; and the bases of the sporophores are sur- 

 rounded by huge masses of protoplasm like the one shown at 

 Fig. 1, Plate XII. Whereas, on leaves taken from the open 

 in dry weather, the fungus does not produce spores in such pro- 

 fusion as to color the leaf spots; no masses of protoplasm are to 

 be found at the bases of the sporophores; and it is rare that im- 

 mature spores can be found attached to the branches of the 

 sporophores. 



BOTANICAL RELATIONSHIP OF THE DOWNY MILDEW 



FUNGUS. 



Botanists have grouped the higher plants into families and 

 given these families Latin names. For example, we have the 

 Gourd Family or Cucurbitaceae, which contains the gourd, musk- 

 melon, watermelon, cucumber, squash, pumpkin and other similar 

 plants. The numerous species of fungi have been grouped into 

 families in the same manner, and so we have the family of smuts 

 or Ustilagineae, which contains all the species of smut fungi, 

 such as corn smut, oat smut, onion smut, etc.; the family of 

 Rusts or Uredineae, which contains the various species of rust 

 fungi, and many other families. 



The cucumber downy mildew fungus lias the Latin name, 

 Plasmopara cubensis, and it belongs to the fa,mily of Downy Mil- 

 dews or Peronosporeae. This is a family which contains many 

 species of fungi injurious to cultivated plants. Some well known 

 examples are: The dreaded potato-blight, Phytophthora infestans, 

 the downy mildew of the grape, Plas^nopara viticola, the spinach 

 mildew, Peronospora effusa, and the onion mildew, Peronospora 

 schleideni. But the downy mildews should not be confused with 

 the powdery mildews, such as gooseberry mildew and the com- 

 mon rose mildew. These are quite different in structure and 

 belong to the family Erysipheae. 



HOST PLANTS. 

 The plant upon which a fungus lives is called its host plant. 

 Plasmopara cuhensis has several host plants, all of which belong 

 to the Cucurbitaeeae. It was originally discovered on a wild 



