220 GENETICS [BoT. Absts., Vol. IX, 



1378. Ubisch, G. von. Anwendung der Vererbungsgesetze auf die Kulturpfianzen. 

 [Application of laws of heredity to cultivated plants.] Naturwissenschaf ten 8: 293-299. 1920. — 

 The application of laws of heredity to improvement of cultivated plants is discussed. The 

 author points out the intimate interrelations of theory and practice. The term Mendelian 

 character is used in a special sense to refer to character differences between individuals and 

 races. Difficulties are met with which are dependent upon the effect of environment on the 

 development of characters, existence of complex factor relations in what appear to be simple 

 character contrasts, and the occurrence of linkage phenomena. Linkage is especially impor- 

 tant in practical work because it may greatly increase the difficulty of securing desired combi- 

 nations of factors. Correlations are physiological and should not be confused with linkage 

 phenomena, which depend upon the location of factors in the same chromosome. — Intelligent 

 plant breeding must take account of biological relations in different plants, particularly fea- 

 tures connected with blooming and setting of seed. When plants are propagated vegetatively 

 seed constancy is not necessary, and a highly heterozygous condition maj'^ be desirable on 

 account of its stimulating effect. Different treatments are accorded seed plants depending 

 on whether they are self-fertilized, cross-fertilized, or self-sterile. Genetic analysis is most 

 readily accomplished in a self-fertilized plant, and illustrative details are given for wheat, 

 oats, and barley. Rye is mostly self-sterile, consequently breeding to an absolutely homozy- 

 gous condition is impossible. In potatoes self-sterility, low fertility, and degeneration follow- 

 ing self-fertilization are hindrances to success in breeding, but statements in the literature 

 cannot be accepted without reservations. There is a possibility of attaining immunity to 

 disease by crossing with wild species. Degeneration in potatoes should be a subject for future 

 solution. In sugar beets genetic analysis is particularly difficult because of the influence 

 of external conditions. The aim of sugar beet breeding is to combine high sugar content with 

 high weight, a very difficult task because both characters are determined by a series of multiple 

 factors. The sugar beet may be crossed with other beet derivatives. — The possibility of 

 improvement depends upon genetic diversity of species; good characters of whole series of 

 forms may then be gradually combined in one. The origin of germinal diversity is not well 

 understood. The idea of gradual change under the effect of environmental conditions conflicts 

 with present conceptions of the nature of the gene and of changes in it. Fortuitous mutation 

 with subsequent selection of favorable mutations may account for progress, but even so-called 

 mutations may often be cases of complex segregations. Reversion to wild type on crossing 

 is an instance of complex factor interaction, of great theoretical interest because it permits 

 of phylogenetic deductions. Advance in knowledge continually widens the circle of phenom- 

 ena subjected to genetic experimentation. — R. E. Clausen. 



1379. Vincent, C. C. Results of pollination studies at Idaho University. Better Fruit 

 14^: 11-15. 3 fig. 1920. — One of the first problems in apple orchard pollination is the detec- 

 tion of varieties inclined to be unfruitful when planted alone. Self-sterility is not a constant 

 character; hence fertility of commercial varieties must be tested locally. Of 50 varieties 

 tested, 18 were found to be self-sterile, 7 self-fertile, and 25 partially self-fertile. In this 

 fruit among varieties of apples, when blossoms are exposed to insect visitation, counts were 

 made on certain branches at flowering time and final counts on June 15 of "fruits set." The 

 percentages for the 4 varieties Wagener, Grimes, Rome, and Jonathan ranged from 46.7 

 to 76 with an average of 63.6; no counts were made at time of harvest. Had harvest counts 

 been made the author estimates a 50 per cent reduction in percentages, bringing the normal 

 set of fruit to approximately 31.8 per cent. If, under favorable conditions, 31.8 per cent 

 constitutes a normal set of fruit when 2 or more varieties are planted together, the majority 

 of varieties tested for self-fertility would not be productive if planted each by itself in large 

 blocks. Two methods of determining self-sterility were tested: 1st, enclosing unopened blos- 

 soms in paper sacks, and 2nd, erecting tents of cheese-cloth over individual trees. The results 

 showed very little difference between the 2 methods. Thermometer readings, within and 

 without the cheese-cloth cages, showed that temperature differences under the 2 conditions 

 were very slight. Seed production is less in self-fertilized fruits than in cross-pollinated 

 fruits. A large number of domestic commercial varieties of apples are self-sterile, and those 



