Band 129. Nr. 25. XXXVI. Jahrgang. IL Bd. Nr. 25. 



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: 



Dr. D. H. Scott. Prof. Dr. Wm. Trelease. Dr. J. P. Lotsy. 



und der Redactions-Commissions- Mitglieder : 



Prof. Dr. Wm. Trelease, Dr. C. Bonaventura, A. D. Cotton, 



ProL Dr. C. Wehmer und Dr. C. H. Ostenleld. 



▼on zahlreichen Specialredacteuren in den verschiedenen Ländern. 



Dr. J. P. Lotsy, Chefredacteur. 



No. 51. 



Abonnement für das halbe Jahr 15 Mark 

 durch alle Buchhandlungen und Postanstalten. 



1915. 



Alle für die Redaction bestimmten Sendungen sind zu richten an: 

 Redaction des Botanischen Centralblattes, Haarlem (Holland), Spaarne 17. 



Gpoom, P., A preliminary inquiry into the significance 

 of Tracheid-Caliber in Coniferae. (The Botan. Gazette. 

 LVII. p. 287-307. 1914.) 



The author gives the following summary: 



1. There is considerable evidence that the width of the spring 

 tracheids in evergreen Coniferae is largely decided by two factors, 

 systematic afifinity and available water supply. So far as the latter 

 is concerned, the spring tracheids are generally narrowest in spe- 

 cies of xerophilous habitat. 



2. In American species of Pinus belonging to section I [Haplo- 

 xylori), Variation in the width of the spring tracheids runs quite 

 parallel with difference of systematic afifinity and of available water 

 supply (including influences promoting transpiration). Thus the first 

 Step in the evolution of this section of Pinus would appear to have 

 been a division into a more xerophilous type (ancestral Paracembra), 

 and a less xerophilous type (ancestral Cembra), and each of these 

 subsections would appear to have undergone similar division into 

 more or less xerophilous groups. that is, into Parva and Balfouria, 

 also Eu-Cembra and Strobus. The two East Tndian species, P. Ge- 

 rardiana and P. excelsa, structurally accord with this theory. 



3. Among American species of Pinus belonging to section II 

 {Diploxylon) , those with narrow spring tracheids are more xero- 

 philous in distribution, while those with the widest tracheids belong 

 to a subtropical or tropical moist climate. Though in general this 

 section of Pitnis Supports the theory given in paragraph 1 , there 

 are in it certain species in which width of tracheid does not appear 

 to correspond with the supply of available water. Such discrepan- 



Botan, Centralblatt. Band 129. 1915. 42 



