116 



currently with the growth of the plant, causing lesions at its base and a 

 withering of its lower leaves, and often its death before or soon after its 

 appearance. Probably the embryo is affected by the fungus in most cases 

 where the seeds do not germinate. The spores exuded from the lesions on 

 the stems, leaves and pods are scattered by the wind and other agents, and 

 infect healthy plants. If the spotted pods are left upon the vines until the 

 seeds are mature the mycelium penetrates some of these seeds, which thus 

 carry the fungus over the winter, making this an important means for the 

 dissemination of the parasite. 



Seed treatment has not been very effective in controlling this disease 

 which, fortunately, with the exception of an occasional epidemic, is not 

 very destructive. Rotation of crops is one method usually recommended. 



Loose Smut of Wheat. 

 Ustilago tritici (Per.) Jens, on Triticum vulgare. 



It was formerly thought that the spores of this fungus became at- 

 tached to the coat of the healthy seed and germinated at the time of the 

 germination of the seed, infection threads from the promycele penetrating 

 the first leaf-sheath, as is the case with stinking smut. But later inves- 

 tigations have made quite certain that the germinating spore infects the 

 pistil of the healthy wheat at flowering time, the mycelium establishing 

 itself within the ovary during its development and remaining dormant in 

 the ripened seed until it had germinated, the mycelium then continuing 

 its own development. 1 This fact explains why the results of seed treat- 

 ment for this species have been negative to so large a degree. 



During the latter part of June, 1907, I inoculated many wheat plants 

 with the spores of U. tritici by dusting the young stigma with the spores. 

 The stigma seemed to be most receptive when quite young. Records of 

 inoculations were kept and heads gathered at varying intervals of time 

 from date of inoculation. A pistil examined one day after inoculation 

 showed that a number of spores adhered to the stigmas and that several 

 had germinated. It was hoped that the point of infection would be ob- 

 served and although the germ tubes of spores were seen directed toward 

 the interior of the stigma, none were seen entering or within. Spores 

 were also germinating on the surface of the ovary and it may be that the 

 point of entrance is through the ovary coat. Of those seeds which were 



1. Brefleld and Falck, K., Flower Infection by Smuts. Untersuch. ges. Gebiet 

 Mykol. 1905, No. 13. Abs. in Bot. Centbl. 101 (1906) No. -8: 212-213. 



