Morphologie etc. — Varietäten etc. • 247 



des anomalies etudiöes, bienqu'elle pui.sse etre favoris^e par les con- 

 ditions ext^rieures, est un phdnomene d'heredite. 



Van der Lek (Wageningen). 



Pearson, H. W., A note on the inflorescence and flower 

 of Gnetiim. (The Ann. Bolus Herbarium. I. p. 152—172. 3pl. 1915.) 



The author draws attention to the need for further study of 

 the structure of the gnetales. He contributes a number of obser- 

 vations on the flower oi Gnetum and discusses the various theoretical 

 views which have been put forward concerning this and the other 

 two genera, Welwitschia and Ephedra. 



The principal points to which he draws attention may be 

 summarised as follows: 



The male inflorescence of Gnetum Gnemon usuall}^ bears one 

 or more complete female flowers. In G. scandens the incomplete 

 female flowers are very small and it is suggested that this species 

 shews a stage in the reduction of the female flower of the male 

 inflorescence which, when carried further, results in the pure male 

 inflorescence of G. africamnn and G. Biichholsianum. Since the 

 incomplete female flowers must be regarded as derived by partial 

 arrest from complete and potentially functional flowers, the former 

 existence of a normally bisexual inflorescence must be assumed. 

 A Suggestion that the primitive inflorescence consisted of an axis 

 bearing a cupule, a ring of male flowers, and a terminal female 

 flower — or a group of which one was terminal — is renewed and 

 supported. Evifience for regarding the female flower as homologous" 

 with a uninodal inflorescence, and its lowest envelope with the 

 cupule, is stated. The male flowers are not regarded as being 

 axillary to the cupule. The general conclusion is reached that the 

 evidence on support of the current view that the male flower is 

 a reduced "anthostrobilus" is insufficient. 



Agnes Arber (Cambridge). 



Pearl, R., The selection problem. (American Naturalist. LI. 

 p. 65—91. 1917.) 



In this paper the writer reviews briefly some of the real 

 evidence about the selection problem which has been accumulating 

 since biologists turned definitely to the experim.ental study of evolu- 

 tion, and definitely away from the glorious, but on the whole 

 unproductive attempt to solve the problems by a priori reasoning. 

 The paper is divided into three parts, one treating the evidence of 

 natural selection, the other the experience of practical breeders 

 and the third one selection experiments. The different views about 

 selection and the röle it played in the process of evolution are 

 reviewed. Two opposed opinions are held. On the one hand is 

 held, that selection on the basis of personal somatic qualities 

 only, as such, in and of itself, has altered hereditary factors in 

 the germ plasm. The opposing view is that selection can only be 

 successful in altering the type when hereditary determiners to 

 produce the desired somatic qualities are already present in the 

 germ plasm. The Opposition here really goes very far back. It is 

 the world-old fight between heredity and environment, nature and 

 nurture, germ and soma. 



The alternative views are presented. In the present State of 

 knowledge nothing is to be gained by mere assertions of opinion 



