June, 1920] GENETICS 335 



1917 from 6 families proved to he homozygous for fullness and 103 proved to l>c heterozygous, 

 a preponderance of homozygous plants, as the expected numhers are 56 and 112. The 103 

 heterozygous plants produced 1.536 tall and 514 dwarf plants, almost an exact ratio of 3 tall 

 to 1 dwarf. — No adequate explanation of the sudden appearance of this dwarf form has yet 

 been found. — J . M, Beal. 



2211. Warren, Ernest. The pure line hypothesis and the inheritance of small variations. 

 South African Jour. Sci. 15: 535-567. PI. 16. 1919. — Author crossed a tall nasturtium (Tro- 

 poeolum tnajus) with large, uniform green leaves and pale yellow flowers as ovule parent with 

 a dwarf variety (T. yninus) with small variegated leaves and red flowers. Eleven of the 

 twenty-one hybrids had over 90 per cent good pollen. The remaining ten had only from 2 to 

 41 per cent good pollen and produced, on the average, fewer seeds, of which a smaller average 

 percentage germinated. The author considers it likely that defective ovules were associated 

 with the bad pollen. Low fertility and poor germination were also encountered on selfing 

 the pollen parent. The tall habit and unvariegated leaves were dominant over the dwarf 

 habit and variegated leaves. Segregation occurred in both cases in approximately a 3 : 1 

 ratio. The two factors were linked in inheritance [the data indicating about 21 per cent cross- 

 overs]. Size of leaves did not segregate in a clear-cut fashion but was correlated closely with 

 tallness and to a less extent with non-variegation, even among those with the same habit. 

 There were clear indications of segregation in regard to yellow chromoplasts and red sap 

 pigment but the mode of inheritance could not be determined from the data, there being a 

 number of seemingly unaccountable cases. The progeny of different Fi plants differed con- 

 siderably in average degree of variegation, leaf width and intensity of red in the flowers. In 

 the last case the correlation between Fi parent and F 2 progeny was found to be 0.435. The 

 author interprets the occurrence of these heritable fluctuations adversely to the pure-line 

 theory. — Sewall Wright. 



2212. Whipple, George Chandler. Vital statistics: An introduction to the science of 

 demography. 12 X 18 cm. v + 517 p., 63 fig. John Wiley and Sens: New York, 1919— The 

 book is an elementary treatment of the methods and material of vital statistics, including 

 chapters on statistical arithmetic, graphs, enumeration and registration, general death rates, 

 birth rates, marriage rates, specific death rates, causes of death, analysis cf death rates, sta- 

 tistics of particular diseases, studies of death by age periods, probability, correlation, and 

 life tables. The book is evidently intended for a popular text book, efforts are made to keep 

 the subject from being "dry," and special emphasis is laid on the real and supposed fallacies 

 of statistics. — Sylvia L. Parker. 



2213. Whitby, Stafford. Variation in Hevea brasiliensis. Ann. Botany 33: 313-321. 1 dia- 

 gram. July, 1919.— Determinations of the rubber-confeent of the latex, the rubber-yield, and 

 the trunk-girth for the individual trees of a population of 1011 7-year old trees being tapped 

 by a V-cut on half the circumference at a level of about 30 inches, and forming an appar- 

 ently normal area of plantation rubber in the Malay States, showed the following results. — (a) 

 The rubber-content of the latex ranged from 23 to 55 per cent. The mean value was 36.58 =*= 

 0.25 per cent. <r 5.86 = t = 0.17 per cent, C.V. 16.02 ± 0.49 per cent, (b) The rubber-yield for a 

 given tree remained approximately constant. The frequency curve referring to rubber-yield 

 showed a marked positive skewness. Mean yield, 7.12 =*= 0.115 grams, a, 5.425 =*= 0.08. Mode 

 (by inspection), 4 grams C.V., 76.19 =■= 1.14 per cent. Coefficient of skewness (on a), + 0.575. 

 As indicating the character of the yield distribution, it is noted that, on the one hand, 9.6 per 

 cent of the trees (trees giving twice the mean yield or more) was contributing 28 per cent of 

 the total yield, and, on the other hand, 13.7 per cent of the trees (trees giving 0.2 gram) was 

 contributing only 2.9 per cent of the crop. The highest yielders in the population were 4 trees 

 giving from 41 to 43 grams per diem, (c) The correlation between trunk-girth and latex- 

 yield is positive, but not very high, being + 0.260 =*= 0.020.—^. Whitby. 



BOTANICAL ABSTRACTS, VOL. Ill, NO. 6 



