No. 3, October, 1921] GENETICS 201 



Normally, not as large a percentage of blooms set fruit in Rome Beauty as in Wagener or York 

 Imperial. Under orchard conditions the set in Rome Beauty is 4.46 per cent, whereas in 

 York Imperial it is 7.87 and in Wagener 8.50. — The relative sterility of 2 varieties may not be 

 judged by a direct comparison of the percentage of fruit set on each, but rather by a compari- 

 son of such set of fruit to the normal set of the variety. In the same way the efficiency of 

 a mutual pollenizer may not be judged by a direct comparison of its effects upon 2 varieties, 

 but rather by a comparison to the normal set of each. While none of the varieties given in 

 the table are entirely self-sterile, they are greatly benefited by cross-fertilization. For 

 Rome Beauty the percentage of set was increased 3J times, York Imperial 14 times, and Wage- 

 ner 7 times. The size of individual fruits was increased by crossing; for Rome Beauty the 

 increase over the size of self-pollinated friiits was 27.8 per cent, and for York Imperial 42.7 

 per cent. In 1914 and 1915 tests the set of fruit from emasculated buds was more than double 

 that from buds not emasculated. Leaving calyx and corolla intact, removing corolla only, 

 or removing both calyx and corolla appeared to make no difference in the results. The prob- 

 able explanation of increased activity in emasculated blooms may be found in the protection 

 it affords against superabundant pollination by the blooms' own pollen. Probably self- 

 pollination frequently occurs naturally before artificial cross-pollination is brought about. 

 Tubes of foreign pollen must then compete with tubes of the flowers' own pollen, with the 

 result that chances of cross-fertilization are lessened. — A table of seed production shows that 

 there are from 2 to 6 times as many seeds in the crossed fruits as in the selfed ones. — The 

 possible presence of toxic secretions from stigmas was investigated, over 200 tests being made 

 in which pollen of several varieties was germinated in stigmatic extracts from the same variety 

 or other varieties. No toxic action was discovered. Thus it is evident that sterility is not 

 a result of inhibition of pollen germination by toxins. — In a 1915 test of the value of cross- 

 fertilization 6 hives of bees were placed in a section of a Rome Beauty orchard, and blooming 

 branches of other varieties were fastened upright in pails of water suspended in the trees; 

 16 trees were observed. At some distance 16 similar trees were used as a check. The bee 

 section produced more than twice as much fruit as did the check section, indicating clearly the 

 value of bees in an orchard. The bee plat more thoroughly self-fertilized than the rest of the 

 orchard would probably have shown some gain, but it is believed that the gain was due pri- 

 marily to the cross-fertilization that must have taken place. — C. S. Crandall. 



1292. Altenburg, Edgar. Interference in Primula sinensis. Amer. Nat. 55: 78-80. 

 1921. — Upon recalculating the linkage data presented in a former paper (Genetics 1: 354- 

 366. 1916), the writer finds, bj'- correcting an error of calculation, that thej"^ indicate inter- 

 ference of about the same degree as found in Drosophila. Only plants with red stigmas were 

 used in this calculation. The total crossing over in the 2 regions was 11.2 and 36.6 per cent; 

 observed double crossovers, 2.9 per cent; coincidence, 2.9-j-4.1, or 0.7; total number of indi- 

 viduals, 1876. — E. G. Anderson. 



1293. AucHTER, E. C, Apreliminary report on apple and pear breeding in Maryland. Proc. 

 Amer. Soc. Hort. Sci. 17: 19-32. 1920 [1921]. — Pear crosses were made in 1905 and in each 

 succeeding year, except 1915, to and including 1917. The aggregate of seedlings grown was 

 1368, representing 10 of the 12 years. Ten varieties appear as parents in 28 crosses represent- 

 ing 17 parental combinations. Kieffer was the female parent in 10 crosses, for which 5 varie- 

 ties supplied pollen, and served as the male parent in 8 crosses on 4 varieties. The report of 

 results is deferred pending fruiting of the seedlings. — Apple crosses were made in each of the 

 12 years 1906-1917. Sixteen crosses of 1910-1911 yielded no seedlings. The 827 seedlings 

 grown represent 22 varieties used as parents in 17 combinations in 45 crosses. This report 

 considers 166 seedlings, from the crosses of early apples in 1907, that have fruited; they repre- 

 sent 11 parental combinations. A table gives, for each group, flowers pollinated, fruits picked, 

 seed production, seedlings transplanted, number fruited, number dead, and number not yet 

 fruited. It appears that 2940 pollinations gave 334 fruits, — 11.36 per cent of the pollinations 

 successful. The average seed content was 4.57. Germination of seeds of the different groups 

 ranged from per cent for 5 seeds from the cross Early Ripe X Williams, to 92.73 per cent for 



