DISEASES OF PLANTS. 545 



mined. Bodies having the characters of thick-walled spiny resting spores have 

 been produceil that had the general appearance and cytological characters of 

 oogonia, but no antheridia have been found. A search for these bodies in cul- 

 tures on blocks cut from potato tubers revealed immature stages of what were 

 considered the same bodies, but none has been found in decaying tubers fol- 

 lowing Phytophthora attacks. Somewhat similar bodies have been found in 

 leaves killed by the fungus, but as yet the authors do not claim that resting 

 spores occur in nature. 



In connection with their investigations some varieties of potatoes have been 

 found much more susceptible to disease than others, and a method of determin- 

 ing disease resistance, which consists of inoculating sterile blocks cut from the 

 flesh of potato tubers with Phytopthora cultures, has given results that are 

 fairlj' comi)arable with those obtained in the field. This method of judging rot 

 resistant qualities is believed worthy of extended application. In general cer- 

 tain standard European varieties were found more highly resistant to the fungus 

 than the standard American varieties. In attempting to determine tlie cause of 

 resistance no definite information was found, but it apparently does not consist 

 in differences in tlie relative acidity or in any other chemical factor that has 

 been determined. 



An extended bibliograi)hy is appended. 



Ustilagineae on Andropogon sorghum in America, A. A. Potter (Abs. in 

 Phytopatholoyii, 2 (1912), A"o. 2, p. 98). — In the course of an investigation on 

 the smuts of America, the author reports having studied. Sphacelotheca reiliana, 

 S. sorghi, and Ustilago cruenta. The latter species has not been previously 

 recognized in American literature. 



Notes on some plant diseases of the sugar cane in the Hawaiian Islands, 

 J. E. VAN DEE Stok (Arcli. Suikerindus. Ncderlarid. Indie, 20 (1912), No. IS, pp. 

 609-631; Meded. Procfstat. Java-Suikerindus., 1912, No. 17, pp. 529-651). — This 

 article is the result of a visit of the author to the Hawaiian Islands in 1911, and 

 gives accounts of a number of diseases of sugar cane, most of which have been 

 previously described by Cobb (E. S. R., IS, p. 843; 22, p. 49). 



Infection experiments with, the powdery mildew of wheat, G. M. Reed 

 {Phytopathology, 2 (1912), No. 2, pp. 81-8T).— In a former paper (E. S. R., 21, 

 p. 641) the author showed that biological specialization has resulted in distinct 

 forms or races of mildews on each of the principal cereals, oats, barley, rye, 

 and wheat. Further studies have shown that different varieties vary in their 

 susceptibility, and in the present paper an account is given of investigations to 

 test the resistance of varieties of wheat to wheat mildew. 



In all, 7S varieties of wheat, representing 9 different species of Triticum, were 

 studied, the inoculation material in nearly every instance being conidia from 

 the Turkey Red wheat. Forty-nine of the 78 varieties gave 100 per cent 

 infection. Fifteen of the remaining ones gave an infection of 70 per cent or 

 higher, while of the remaining 14 varieties, 4 were infected to the extent of 

 from 50 to 70 per cent, 6 gave only slight infection, and 4 wei'e immune. 



The greater number of varieties of T. tmlgare were found susceptible to mil- 

 dew, while the immune varieties belonged to the species T. dicoccum and T. 

 vuJgare. The varieties of the different species which showed a .marked re- 

 sistance to mildew were all spring varieties. In some cases where the same 

 variety was grown as a winter and spring wheat, the winter variety was sus- 

 ceptible while the corresponding spring variety was relatively or entirely 

 immune. 



There was no evidence to indicate a specialization of wheat mildew within 

 the genus on its various hosts. 



