224 



PLANT DISEASES 



not be sown for some years. The disease appeared in one 

 instance after a period of twelve years' rest, due presumably 

 to smut-spores still present in the soil. 



Thaxter, Ann. Rep. Conn. Agric. Expt. Station, p. 129, 

 pi. 2 (i8go). 



Weed, Fungi and Fungicides, p. 152. 



COLCHICUM SMUT 



{Urocystis colchici, Rab.) 

 This smut often forms long rows of black, powdery 

 streaks on the leaves of Cokhinnn {Colchicum autumnale). 



Fig. 54. — Urocystis colchici. i. Portion of a diseased leaf, 

 nat. size; 2, a single sorus, slightly mag. ; 3, spores, X300. 



Muscari racemosum, M. comosum, Scilla bifolia, Allium 

 rotundum, A. cepa, A. magicum, and Paris quadrifolia. 



