244 AGRICULTURAL EXPERIMENT STATION. [Jan. 



proposed to give annually in these reports special detailed 

 instructions for the treatment of some group of diseases 

 caused by fungi whose life histories are so similar that the 

 same directions will apply to all. The symptoms of each 

 disease and its effect on the diseased plants will be described, 

 and enough of the life history of the parasite will be given 

 to make clear the reasons for the treatment prescribed. 



The group chosen for the present report is one of the best 

 known as to the life history of its members, some of which are 

 among the most easily avoided of all the fungi. It will, there- 

 fore, serve as an excellent introduction to the subject. Further- 

 more, the simplicity of the preventive treatment for some of 

 these diseases will serve to tempt the reader to undertake it, 

 and its striking efficacy will encourage the beginner to try 

 the more laborious treatment for other troubles. The diseases 

 in question are those known as Smuts. (See Plate I.) 



Of the large number of smut fungi which attack plants of 

 all sorts, the number of those which are sources of loss to 

 Massachusetts farmers to such an extent as to deserve 

 mention here is five or six. They are those which cause the 

 diseases known as the loose smuts of oats, barley and corn, 

 and the leaf smuts of rye and of onions. 



The loose smuts are peculiarly harmful, because the black 

 smut-masses are formed only in the seeds or grains, the very 

 part for which the plants are cultivated. These smuts of 

 oats, barley and wheat have been regarded until lately as 

 belonging to a single species known as Ustilago segetum 

 (Bull.) Ditm. ; but those who have studied them most care- 

 fully now consider that they include four species, distin- 

 guished by differences in spore germination, and by their 

 restriction to particular hosts and their inability to attack 

 others. They are called respectively Ustilago Avenue 

 (Pers.), on oats, U. Hordei (Pers.) and U. nuda, (Jensen) 

 K. & Sw., on barley, and U. Tritici (Pers.), on wheat. 

 As the oat smut has been studied most and is best known, 

 and is also perhaps the form which causes most loss in Massa- 

 chusetts, it may be described here as a general type (Fig. 1.) 



This fungus can penetrate only the very young tissues of 

 its host plant, and is harmless to tissues whose outer cell 

 walls have begun to harden. To be effective, the fungus- 



