Band 113. Nr. 17. XXXI. Jahrgang. I. Bd. Nr. 17. 



Botanisches Centralblatt. 



Referirendes Organ 



der 



Association Internationale des Botanistes 

 für das Gesamtgebiet der Botanik. 



Herausgegeben unter der Leitung 

 des Präsidenten: des Vice-Präsidenten : des Secretärs: 



Prof. Dr. Ch. Flahault. Prof. Dr. Th. Durand. Dr. J. P. Lotsy. 



und der Redactions-Commissions-Mitglieder: 



Prof. Dr. Wm. Trelease, Dr. R. Pampanini, Prof. Dr. F. W. Oüver 



und Prof. Dr. C. Wehmer. 



von zahlreichen Specialredacteuren in den verschiedenen Ländern. 



Dr. J. P. Lotsy, Chefredacteur. 



Nr. 17. 



Abonnement für das halbe Jahr 14 Mark 



durch alle Buchhandlungen und Postanstalten. 



1910. 



Alle für die Redaction bestimmten Sendungen sind zu richten an: 

 Redaction des Botanischen Centralblattes, Leiden (Holland), Bilder- 

 dijkstraat 15. 



Blackman, V. H., Alternation of generations and onto- 

 geny. (New Phytologist VIII. 5/6. p. 207—218. 1909.) 



This paper was suggested by the discussion on "Alternation of 

 Generations" at the Linnean Society reported in the New Phytolo- 

 gist Vol. VIII p. 104. The author finds great difficulty in accepting 

 Dr. Lang's theory of ontogeny, and the present contribution deals 

 chiefly with the question of the physiological reason for the diffe- 

 rence between gametophyte and sporophyte. In Dr. Lang's view 

 the differences in the two generations are supposed to be the result 

 of the external conditions under which their development is initiated. 

 He considers that the "germ cells", (the fertilized egg and the spore), 

 when formed are perfectly neutral, and without any innate tendency 

 to produce either gametophyte or sporophyte. Dr. Blackman on the 

 other hand holds that there are inherent differences between the 

 germ cells which cause them to develope along different lines. If 

 we accept this view there are two possible alternatives, a. That the 

 germ cells behave differently because of their chromosome number, 

 haploid and diploid respectively. b. That the germ cells behave 

 differentty because of their different position in the life-cycle, i. e. 

 that in their development they bave received different tendencies. 

 Dr. Blackman considers that the evidence is against the first alter- 

 native. "Both general considerations and actual evidence clearly 

 show that the assumption of the relation of cytological character 

 and the two types of reproduction is not warranted." Evidence from 

 Dictyota, and the Uredineae, and from animals which shew two 

 body forms, such as certain insects and Foraminifera , points to the 



Botan. Centralblatt. Band. 113. 1910. ' 28 



