52 Biologie, — Morphologie etc. — Varietäten etc. 



period it has good chances of reaching the natural size ofthe species. 

 This is attained in different ways by the different species: 



a. The oaks throw the stress of growth into a Single series of 

 buds and so prolong the main axis at the expense of lateral branches 

 that the tip of this axis may be lifted beyond the reach ofthecattle 

 in comparatively few years. 



b. The haws and apples put out a large number of approximately 

 equal branches forming a close network about the center of the 

 tree, which is finally so far removed from the attacks of the cattle 

 that it may grow unmolested. This is a much slender method than 

 the one adopted by the oaks but seems to be somewhat surer as 

 judged by the number of successful individuals. 



c. The elms have given up the attempt to reach independence 

 without the help of some other plant but because of their persistence 

 raany of thera are in time given the necessary protection. 



While thorns are undoubtedly a factor in the escape of some 

 species from the cattle their importance may easily beoverestimated; 

 the apples are apparently quite as successful as are the haws but 

 are not provided with this armament. Jongmans. 



Lubimenko, V., Nouvelles recherches sur les pigments 

 des chromoleucites. (C. R. Ac. Sc. Paris. CLX. p. 277—280. 

 1915.) 



L'evolution chimique des pigments contenus dans les chloro- 

 leucites au cours de leur transformation en chromoleucites aboutit 

 ä la formation d'un grand nombre de substances color^es qui se 

 rattachent ä la Carotine, la xanthophylle et leurs deux isomeres: 

 la lycopine et la rhodoxanthine, L'apparition des substances inter- 

 m^diaires entre ces quatre formes principales ainsi que la formation 

 des deux derniers pigments rouges, qui n'existent pas dans les 

 chloroleucites, doit etre attribuee aux deux Processus chimiques 

 oppos^s, l'oxydation et la reduction, qui remplacent Tun l'autre au 

 cours du developpement du tissu chlorophyllien et qui attaquent 

 l'appareil assimilateur. Nous ne savons pas exactement ce qui se 

 passe avec les pigments des chloroleucites pendant leur activite 

 assimilatrice; mais il est tres probable que l'oxydation est contre- 

 balanc^e dans ce cas par la reduction, ce qui donne comme resultat 

 une stabilite apparente de la chlorophylle et des pigments jaunes 

 qui l'accompagnent. Jongmans. 



Davis, M. B„ Oenothera neo-Lamarckiana, hybrid of O. francis- 

 cana Bartlett X ^- biennis Linnaeus. (American Naturalist. 

 L. p. 688-696. 1916.) 



The authors researches about artificially made hybrids within 

 the genus Oenothera, have yielded results quite as satisfactory as 

 he had hoped. Oenothera neo-Lamarckiana is a name which the 

 writer proposes for a synthetic hybrid that so closely resembles 

 O. Lamarckiana de Vries that the writer does not believe syste- 

 matic botanists could separate it from the latter by characters 

 which would enter into a specific description. The parents of his 

 hybrid are 0. biennis from the sand dunes of Holland an O. 

 franciscana f ro m California. 



In the group of O. neo-Lamarckiana there is some Variation, 



