278 DOWNY MILDEW OF MAIZE. 



Sclerospora macrospora Sacc. occurs on maize and on many 

 other grasses in Italy 1 . This species is characterised by the absence 

 of a conidial stage and the formation of large oospores within the 

 affected tissues. Diseased plants can only be distinguished from 

 healthy by malformations of the inflorescence, similar to those 

 observed in Pennisetum and Setaria attacked by S. graminicola. 

 There is no alteration in the colour, thickness or consistency of 

 the leaves and no disintegration of the tissues such as causes the 

 peculiar shredding of the leaves noticeable as a result of the action 

 of S. graminicola. The symptoms described by Italian observers 

 differ so essentially from those observed in Java and India that 

 it appears to be unlikely that the same fungus can be the cause 

 of both. It is possible, of course, that these differences are due 

 to the occurrence of the fungus in two different stages in Europe 

 and Asia and that, if the conidial stage of S. macrospora were 

 to develop in Europe, the affected plants would resemble those 

 observed by Raciborski and myself. Until true oospores are 

 obtained in the eastern form, it will not be possible to decide this 

 point, but in the meantime it appears to be improbable that the 

 cause of " sleepy " disease is S. macrospora. It is stated in Duggar's 

 ' ' Fungus diseases of Plants ' ' that S. macrospora has been reported 

 on maize in the United States by Fairchild. I have not been able 

 to find the reference and it is not included in Wilson's Host Index of 

 North American Peronosporales 2 . 



With S. graminicola there are many points of similarity, espe- 

 cially now that a variety of this species is known which has lost 

 the power of zoospore formation. The mildew of Andropogon 

 Sorghum, in the 3rd form of attack described by Mr. Kulkarni 

 in the preceding paper closely resembles that of maize. There 



1 See Cugini G. & G. B. Traverse La Sclerospora macros pora Saec. parassita della Zea 

 Mays L. Stazione Sperimentali Agrarie Italiane, XXXV, 1902, p. 46, D'Ippolito, G. & G. B. 

 Traverso. La Sclerospora macrospora Sacc. parassita delle infiorescenze virescenti di Zea 

 Mays L. ib., XXXVI, 1903, p. 975. D'Ippolito, G. Osservazioni intorno ad alcuni miovi casi 

 di frondescenza nelle infiorescenze di Granturco, ib., XXXVIII, 1905, p. 998. 



2 Wilson G. W. Studies in North American Peronosporales, IV, Host Index. BuU. Torrey 

 Bot. Club, XXXV, 1908, p. 543. 



