Notes on Some Diseases of Grasses. 



BY W. C. STEVENS. 



With Plates XI, XII and XIII. 



Grasses are subject to attacks from various minute parasitic plants, 

 resulting to the host in diminished vigor, accompanied by the destruc- 

 tion of tissues or the formation of abnormal growths. The number 

 of these parasites catalogued for the grass family in Farlow and Sey- 

 mour's Host Index is between four and five hundred. For corn alone 

 sixty-nine parasites are listed, for wheat fourteen, and for oats six. 

 This is for extra-tropical America. 



One who gives only a passing notice to plants as he walks through 

 the fields would hardly surmise, when vegetation is in its prime, that 

 here and there disease is sapping the vitality of the sturdy grasses. 

 But now, in December, when the blanched leaves and culms stand out 

 above our first light snows, the scars of summer conflicts become con- 

 spicuous. Very evident are the rusts on Panicimi virgattwi., Andj-o- 

 pogon furcatiiz, Bouteloiia racemosa, and Tripsaciim dactyloides ; 

 while growing between clumps of these, large patches of Setaria glauca 

 show leaves flecked over with blighted spots. The standing spikes of 

 Elymus Canadensis and E. virginicus are interspersed with the slen- 

 der black sclerotia of Claviceps purpurea, and frequently the glumes 

 are glued together by the pink masses of a Fusisporium, hardly less 

 destructive to the ovaries than the Claviceps. On the borders of the 

 grain fields, among the few stalks of wheat and oats left standing by 

 the reaper, the not infrequent blackened spots where the ovaries or 

 glumes should have been, and the malformed masses in the standing 

 corn suggest that, though unnoticed by the farmer, the loss in the 

 aggregate, due to smut, has been no trifling amount. 



If one is amazed at the Ipng list of parasites in the Host Index, he 

 is probably no less astonished when he notices for the first time their 

 prevalence by his doorstep and through his fields. The fungus dis- 

 eases of plants have been studied for many years, and activity in this 

 line of research is now greater than ever. Investigations of the life- 

 histories of parasites have brought to light some surprising facts and 

 have led to the more intelligent application of remedies. These pres- 

 ent notes relate chiefly to the visible effects of the parasite on the host. 



(123) KAN. DNIV. QTTAR., VOU I., NO. 3, JAN., 1893. 



