!42 The American Naturalist. [February, 



symptoms all of the plants remained sound, ripening normal ears. The 

 fourth experiment, with still larger plants, gave wholly negative 

 results. The heart of the plant proved immune, and normal ears 

 developed. In another experiment female inflorescences were infected 

 as soon as there was any indication of a forming ear, the Nahrlosuug 

 containing the conidia being injected into the narrow opening between 

 the ligule and the axis. Smut pustules appeared in great numbers 

 within 18 days but only on the parts which were actually reached by 

 the injected fluid. Another experiment was made when the ears were 

 in blossom. All the kernels became smutty and single ears reached 

 the size of a child's head. In another experiment varying amounts of 

 the lower part of the ear were protected from the fungous spray by 

 wrapping them in blotting paper. In this case only the exposed ker- 

 nels became smutty, showing again conclusively that the infection is 

 purely local. The silk though much exposed to the conidial spray 

 showed not the least trace of injury, having passed out of the meristem- 

 atic stage. In still another experiment the kernels of the ear were 

 sprayed with the smut conidia when they were more than } grown. 

 The result was wholly negative ; no smut appeared. Another experi- 

 ment showed that the adventive aerial roots can also be infected if 

 sprayed in an early stage of their growth. In short, any meristematic 

 part of the maize plant is liable to direct infection and this is made 

 easy by the fact, which is also Dr. Brefeld's discovery, that the com 

 smut fungus, unlike that of oats and sorghum, is richly provided with 

 aerial conidia, which are easily carried or blown from the soil to any 

 part of the plant. The consequent desirability of keeping the soil of 

 corn fields free from smut spores, by removing and burning all smut 

 pustules before they have ripened and shed, must be apparent to all. 

 The corn smut spores seldom germinate in water, as is well known, and 

 infection of the plant probably takes place only when the latter have an 

 opportunity to germinate in the soil and produce the aerial conidia, this 

 germination in the soil being greatly favored by the presence of dung. 

 The volume contains VI, 98 pages of text and 5 lithographic plates, 

 mostly colored.— Erwin F. Smith. 



