19181 DISEASES OP PLANTS. 749 



natalcnsis. Blossom-end rot of oranges may be due to a Fnsarium. A black 

 rot, ascribed to Alternaria citri, Is not regarded as of very great importance 

 at this time. Citrus canlver is not yet known to have been brought to Porto 

 Rico from the neighboring mainland. 



Cytospora sacchari is a comparatively new disease of sugar cane, the well 

 marked symptoms of which are briefly described. Root disoa.se of sugar cane 

 is a trouble a.scrlbed to a number of organisms readily attucking the native 

 cane. All the organisms yield to the same treatment. 



A mold of cigars was found to yield Aspergillus sp. (ii hliic-groen form), 

 A. flavus, Cladosporium herbarum, Penicillium sp., and Fusarium sp., all prob- 

 ably saprophytic in the material used to fasten the wrapper. 



Prickly pear near the southern coast is attacked by a fungus, apparently 

 Diplodia opuntice. 



Leaf spot (Cercospora citrullina) of watermelon was noted near San Juan. 



A defoliating leaf .spot of cowpeas is referred to C. vignm. 



Parasitic Rhizoctonias in America, G. L. Peltier (Illinois Sta. Bui. 189 

 (1916), pp. 281-390, figs. 23; abs., pp. 4). — In connection with a serious stem 

 rot of carnations due to Rhizoctonia, the author has conducted an investiga- 

 tion of the di.seases of vegetable, field, and iloricultural crops which are caused 

 by Rhizoctonia, the primary object being to determine whether infection is 

 brought about by one or more than one species of Rhizoctonia. 



It is stated that there are recognized in America two species of truly para- 

 sitic Rhizoctonia, R. solani, which is widely distributed on a great number of 

 hosts, and R. crocorum, which is at present limited in its distribution to alfalfa 

 and potato tubers. A third species, Corticium ochroleucum, is found on loaves 

 of pomaceous fruit trees, while a fourth species. Isolated from damped-off 

 onion plants, is considered of questionable parasiti.sri. 



So far, the author has found that about 165 species of plants have been 

 listed as subject to attack by R. solani. This list includes mo.st floricultural 

 plants, vegetable and field crops, herbaceous plants, and many weed.s. From 

 inoculation experiments conducted with a large number of types of plants, the 

 author concludes that all the strains studied can be included under the one 

 form R. solani. These investigations show that the virulence of R. solani is 

 very variable, as is also the degree of resistance of the various host plants. 

 No marked specialization was noted in any of the strains of the fungus. A 

 certain vigor of mycelium was found to be required before R. solani is able 

 to attack the plant. A high temperature (88° P.), together with too little or 

 too much moisture determines to a large degree the virulence of the different 

 strains. This fungus is said to become a dangerous parasite only under certain 

 conditions. 



An extensive bibliography is given. 



The susceptibility of grains to smuts and rusts, O. von Kiechnkb (Fiihling's 

 Landw. Ztg., 65 (1916), Nos. 1, pp. 1-27; 2, pp. Ifl-12; S-Jt, r>P. 92-i57).— The 

 results of te.sts with a very large number of varieties of different agricultural 

 grains are detailed and tabulated as regards thejr susceptibility to rusts and 

 smuts with a discussion of the various factors predisposing to attack. A 

 bibliography is appended. 



Resistance of wheat to rust, O. Comes (Ann. R. Scuola Sup. Agr. Portici, 2. 

 ser., 12 (1914), PP- 419-473). — This statement deals with rusts and other para- 

 .sitic injury to wheat as related to stock, breeding, locality, soil, seeding time, 

 and sap constitution. 



Treatment of winter wheat against Fusarium, Penicillium, and stinking 

 smut, L. HiLTNEB (Prakt. Bl. Pflanzenbau u. Schutz, n. ser., IS (1915), Nos. 8, 



