Band 104. Nr. 5. XXVIII. Jahrgang. I. Bd. Nr. 5. 



Botanisclies 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. R. v. Wettstein. Prof. Dr. Ch. Flahault. Dr. J. P. Lotsy. 



und der Redactions-Comniissions- Mitglieder : 



Pro;f. Dr. Wm. Trelease und Dr. R. Pampanini. 



von zahlreichen Specialredacteuren in den verschiedenen Ländern. 



Dr. J. P. Lotsy, Chefredacteur. 



Abonnement für das halbe Jahr 14 Mark 



i durch alle Buchhandlungen und Postanstalten. 



*&' 



1907. 



Alle für die Redaction bestimmten Sendungen sind zu richten an Herrn 

 Dr. J. P. LOTSY, Chefredacteur, Leiden (Holland), Rijn- en Schiekade n3. 



Hill, T. G., On the Seedling Structure of Certain Pipe- 

 rales. (Annais of Botany. Vol. XX. 1906. p. 161 — 175. With one 

 plate and three diagrams in the text). 



The transition in structure from stem to root is described in 

 several species of the Piperaceae and Sanruraceae. In Piper cornifo- 

 lium the basal region of each seedleaf contains one large collateral 

 bündle. While passing down the petiole the phloem is resolved into 

 two masses bounding the xylem on each side, and the xylem under- 

 goes rotation so that the protoxjdem becomes exarch. At the cotyle- 

 donary node the two cotyledonary bundles pass towards the centre 

 of the axis and anastomoses take place between their phloems and 

 the epicotyledonary traces. Finally two phloemgroups are formed 

 and a typical diarch root results. 



In Peperomia eburnea and Pep. pelhicida the bundles fuse 

 together at the distal end of the cotyledonary petiole to form one 

 Strand in which, while passing down the petiole, the phloem gradually 

 forms two groups of elements. In the stem the metaxylem generally 

 travels inwards and leaves the protoxylem in an exarch position; 

 usually there is no definite rotation. The phloem groups fuse and a 

 diarch root is formed. The plumular bundles are unimportant and 

 the vascular tissue of the root is derived chiefly from the cotyledons. 



In Pep. polystachya four epicotyledonary Strands are formed as 

 the result of fusions. They occur two on one side and a similar pair 

 on the other side of a line joining the two incoming cotyledonary 

 traces. In the latter the protoxylem is exarch and the phloem some- 

 what bilobed. As they approach the axis the phloem divides into 



Botan. Centralblatt. Band 104. 1907. 8 



