6. Vererbungslehre. 387 



mines, m and f absence of M or F) is opposed by the difficulty of females 

 producing male offspring parthenogenetically. Ref.] Under „Intermediates" 

 blended inheritance is dealt with, and it is shown that some cases of apparent 

 blending are due to the coexistence of two or more allelomorphic paris which 

 react upon one another. The cases which appear to offer genuine exceptions 

 to Mendel 's Law are exceedingly rare. In the chapter on Variation and 

 Evolution the author discusses the relation of the mutation theory to that of 

 Natural selection, and takes bis chief examples from cases of Mimicry in 

 butterflies. He concludes that mimetic resemblance has, in certain cases of 

 least, arisen by mutation, and that although such mutations may have been 

 preserved by natural selection, and increased relatively to the parent form, 

 they cannot have arisen by gradual selection of small fluctuations. In the 

 section on the economic bearings of Mendelism, the success that has been 

 achieved in improving wheat is described, and an account is given of Jo- 

 hannsen's work on „pure lines". The final chapter is devoted to Mende- 

 lian characters in Man. Don caster (Cambridge). 



1060) Bateson, W. and R. C. Punnett, On the Inter-relations of 

 Genetic Factors. 



(Proc. Roy. Soc. B 84,568. p. 3—8. 1911.) 



Doncaster (Cambridge). 



1061) OliTer, G. W., New Methods of Plant Breeding. 



(American Breeders' Magazine 1,1. p. 21 — 30.) 



0. gives a detailed description of his methods for cross pollinating lettucs 

 and alfalfa as illustrations of methods applicable to flowers whose minute 

 sexual organs are so arranged that ordinary methods are precluded. In both 

 lettuce and alfalfa emasculation without injury to the pistil is impossible. 

 As a Substitute the flower is depollinated after the anthers dehisce and be- 

 fore the pollen tubes have time to penetrate into the Stigma. The depollination 

 is accomplished by allowing a tiny stream of water from a chip blower to 

 play upon the stigma for several minutes, until every grain of pollen is removed. 

 The water which clings to the flower is then blotted up with filter paper. 

 When the lettuce flower opens the pistil lengthens pushing the pollen from 

 the already dehisced anthers out of the stamen tube. The stigma is thus 

 covered with pollen when it appears. When the two lobes of the stigma 

 expand they are quite exposed and depollination by the above method is simple. 

 Early maturing flowers should be selected for cross pollination. The depolli- 

 nated flowers are pollinated by applying with a slight circular motion a pollen 

 covered stigma from a freshly opened flower of the proposed male parent. 



In alfalfa the anthers dehisce in the unopened bud. The pollen is in- 

 operative until the sexual column is sprung against the banner and the pollen 

 grains thus imbedded in the stigma. 3 or 4 freshly opened flowers just below 

 the largest bud are selected. Their sexual columns are as yet unsprung. The 

 pointed half of a small pin is placed against the base of the keel and drawn 

 toward the banner. The pin is brought gradually toward the banner until 

 it rests against it. The sexual column rests against the pin just in front of 

 but free from contact with the banner. The flower is now depollinated by 

 a stream of water, dried and pollinated. The pollen may be applied with a 

 flat pin or a cameis hair brush moistened with thin syrup. After pollination 

 the pin is withdrawn and the stigma rests in its normal position against the 

 banner. M. R. Curtis (Orono). 



