Entomological Xotes. 321 



check the growth of the mycelium on the leaf. The injury that 

 the Uncinula does to the grape is, that it covers the leaves, which 

 in a certain sense may be said to be the respiratory organs of a 

 plant, so that the necessary supply of light and air is shut off. 

 The growth of the fungus may be checked by the use of sulphur 

 strewn over the plants. "We must also consider how the disease 

 is propagated from one plant to another. The conidial spores 

 already described are light and easily blown from one plant to 

 another. Wherever they fall, if the weather is only moist enough 

 they begin to send out threads, which form the mycelium of a 

 new Uncinula. The threads only grow to any length, as far as 

 we yet know, when the spores have fallen on or near grape vines. 

 From this we can infer that the Uncinula does not live entirely 

 upon material found in the air, or accidentally on the surface of 

 the grape leaves, but that it also requires some peculiar substance 

 produced only by the grape plant. A great many of the species 

 of fungi, however, which are botanically closely related to the 

 Uncinula, are not limited to the plants of a single genus, but 

 grow indifferently on plants which are not nearly related 

 botanically. 



Another question also arises. How does the fungus survive the 

 cold of winter? The conidial spores which can spread the dis- 

 ease rapidly are killed by the cold. The round, black bodies 

 which contain the winter spores are much tougher. The winter 

 spores are not ripe till late in the autumn, and fall to the ground 

 with the leaves on which they are growing. They remain dormant 

 during the winter, and when spring comes, germinate and make 

 their way into the nearest grape vines. It would not be unwise 

 in the autumn to collect and burn all the grape leaves, that is, as 

 far as practicable, in districts which have in the summer suffered , 

 from the Uncinula. In this place we should bear in mind what 

 has been said about the black knot extending from wild species 

 to the cultivated. This blight can extend in a similar way, as it 

 is found on wild vines, but as far as we yet know the fungus does 

 not grow on any wild plants except grape vines. 



If we turn now to the Peronospora, which grows on grape vine?, 

 we see that the preventive measures, which in the case of the 

 21 — IIort. 



