Band 137. Nr. 4. XXXIX. Jahrgang. I. Bd. Nr. 4. 



Botanisches Centralblatt 



Referierendes 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, 



Prof. Dr. C. Wehmer und Mag. C. Christensen. 



von zahlreichen Specialredacteuren in den verschiedenen Ländern. 



Dr. J. P. Lotsy, Chefredacteur. 



No. 4. 



Abonnement für das halbe Jahr 15 Mark 

 durch alle Buchhandlungen und Postanstalten. 



1918. 



Alle für die Redaction bestimmten Sendungen sind zu richten an: 

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



Gwynne-Vaughan , D. T., Observations on the Anatomy 

 of the Leaf in the Osmundaceae. (Ann. Bot, XXX. W CXX. 

 p. 487—493. PI. XTII. Oct. 1916.) 



The author believes that the primitive leaf-trace of the Ferns 

 was a solid elliptical mass of xylem, with two protoxylems, mesarch 

 in Position, these being presumably derived from a Single, mesarch 

 protoxylem of a still earlier stage. The short axis of the ellipse 

 corresponded to the median plane of symmetry of the leaf and the 

 xylem was probably completely surrounded by phloem. 



From such a form the Zygopteridean type of trace can be evol- 

 ved; the process would seem to have begun by the Substitution of 

 parenchyma for the tracheides on the outside of the two protoxy- 

 lems; the parenchyma thus developed forms two lateral bays imp- 

 inging on the tracheides. A further complication, possibly connected 

 with the erect habit of the leaves, is the development by some 

 Zygopterideae of four rows of pinnae. On the other band the 

 C-shaped trace, the numerous varieties of which are so characte- 

 ristic of the Ferns, might arise by the development of parenchyma 

 instead of tracheides on the adaxial side of the protoxylems. 



The author regards it as probable that the original mode of 

 branching of the primitive elliptical trace involved the elongation 

 of the immersed protoxylems in the direction of the long axis of 

 the trace, foUowed by the division of the elongated protoxylem. 

 The small, protruding mass of xylem, including the outer of the 

 two resulting protoxylems, would then pass out into the branch- 

 trace. The investigations under consideration were made with the 

 object of ascertaining whether the C-shaped trace retained any pri- 

 mitive features in its branching. The simplest form of departure of 



Botan. Centralblatt. Band 137. 1918. 4 



