Ji^n] FIELD CROPS. 531 



taining many degenerate plants, as even the normal plants in such a field may 

 produce worthless progeny. Mosaic is transmitted through the seed and, owing 

 to the difficulty of diagnosis, threatens to become an important factor in seed- 

 potato production. In view of these observations it is doubtful if any method 

 of selection can entirely prevent the degeneration of potato varieties under 

 certain conditions due to the " running out " of the seed. 



Som.e disappointing seed potatoes, P. H. Hall {New York State Sta. Bui. 

 ^22, popular ed. {1916), pp. 8, figs. S). — This is a popular edition of the above. 



Potatoes, C. A. Zavitz {Ontario Dept. Agr. Bui. 239 {1916), pp. 88^ figs. 28).— 

 This bulletin is a popular discussion of the production of potatoes in the Province 

 of Ontario, including cultural methods, varieties, fungus diseases, insect pests, etc. 



Correlative characters of the rice plant, H. O. Jacobson {Philippine Agr. Rev. 

 [English Ed.], 9 {1916), No. 2, pp. 7//-IJ9). — In a study of rice varieties grown 

 on the lowlands of the Philippines a great quantity of data was collected In 

 correlation studies made in an effort to determine the relative values of the 

 most apparent characters, especially in their relation to the period required 

 by a variety to reproduce itself and to the degree of reproduction. Numerous 

 character correlations were studied and the data are given in tabular form 

 and discussetl in detail. Some of the most striking results were as follows : 



The length of the growing period of rice, if not less than 120 nor more than 

 180 days, has no appreciable effect on yield. Extra early maturity is to be 

 had at the expense of yield. Late maturity is conducive to loss through 

 disease, insects, etc. A variety that tillers freely produces more grain per 

 hectare than one that does not; but when rice is transplated tillering can be 

 largely regulated by the number of plants set in the hill. Tillering, the number 

 of gi-ains per panicle, and grain size are compensating characters. The long 

 period of development in the rice plant permits of environmental influences not 

 met with in such plants as oats or barley. It appears that the medium charac- 

 teristics, and not the extremes, result in the highest consistent yields. 



The weight of rice grains, H. O. Jacobson {Philippine Agr. Rev. [English 

 Ed.}, 8 {1915), No. 4, pp. 289-291) .—The weights of seed from three different 

 sections of the panicle for 58 varieties of Philippine rice are reported. 



An early reference to Philippine rice varieties, H. O. Jacobson {Philippine 

 Agr. Rev. [English Ed.1, 8 {1915), No. 4, pp. 292, 293).— This is a brief account 

 of some early descriptions of Philippine rice varieties. 



A Philippine wild rice, H. O. Jacobson {Philippine Agr. Rev. [English Ed.], 

 8 {1915), No. 4, pp. 294. 295, pi. 1). — This is a description of a Philippine rice 

 identified as Oryza manilensis. 



The causes of low yields of rice in the Philippines, H. O. Jacobson {Philip- 

 pine Agr. Rev. [English Ed.] 8 {1915), No. 4, pp. 262-272, pis. 4)-— A number of 

 factors that tend to decrease the yield of rice in the Philippines are discussed and 

 recommendations made for overcoming them. The most important factors are 

 considered to be (1) lack of irrigation essential to the successful production 

 of the varieties grown, (2) lack of uniformity in varieties, and (3) lack of the 

 proper cultural methods. 



Methods used to improve rice culture in the Philippines, H. O. Jacobson 

 {Philippine Agr. Rev. [English Ed.], 8 {1915), No. 3, pp. 190-206, pis. 3).— This 

 article classifies the rice varieties in the Philippnes as upland and lowland, 

 and describes the cultural characteristics of each group. Cooperative methods 

 and station methods for variety tests are described, together with extension 

 methods employed to acquaint the rice farmers with the improved varieties 

 and methods of cultivation. 



