— 145 — 



bundles can early be discerned in dicotyledonous woody plants or 

 in old forms, it is clear that the evidence for the hypothesis of a 

 preliminary continuous cylinder is not of great value. It is much 

 more probable, in my opinion, to admit, that, when in recent forms, 

 the woody cylinder is split up into separate bundles this develop- 

 ment is not anything new, but only a return to an older stage, an 

 isolation of the fundamental conducting tissue, the bundles. 



I admit that the presence of separate bundles in the young 

 stems of the arboreous plants does not directly involve any ab- 

 solute argument against the American hypothesis because these cell- 

 groups can be explained in favour of it. But in connection with 

 other facts mentioned here, especially the early phylogenetic oc- 

 currence of free bundles, and, supported by general considerations 

 upon the origin of the bundles in the leaves and the relations of 

 these to the bundles in the stems — problems which need further 

 investigations — this presence of separate bundles in the buds of 

 the arboreous plants seems to corroborate the view adopted here 

 that the vascular bundles are of fundamental significance for the 

 building up of the stem-cylinders. 



April 1919. 



List of Literature. 



Bary, A. de: Vergleichende Anatomie der Vegetationsorgane.... 1877. 

 Bailey, I. W. : The relation of the leaf-trace to the formation of compound 



rays in the lower Dicotyledons; Annals of Botany, Vol. XXV, 1911. 

 Bailey, I. W. : The evolutionary history of the foliar ray in the wood of 



the Dicotyledons and its phylogenetic significance ; Ann. of Botany, 



Vol. 26, 1912. 



Eames, A. J.: On the origin of the herbaceous type in the Angiosperms; 



Ann. of Botany, Vol. XXV, 1911. 

 Flot, Léon: Recherches sur la naissance des feuilles et sur l'origine foliaire 



de la tige; Revue gén. de Botanique. Tome 19, 1907. 

 Groom, Percy: The evolution of the annual ring and medullary rays of 



Quercus; Ann. of Botany, Vol. XXV, 1911. 

 Hanstein, J. v.: Ueber den Zusammenhang zwischen der Blattstellung 



und dem Bau des dicotylen Holzringes. Pringsheims Jahrbücher, 1, 1858. 

 Jeffrey, Ch. Edw. : The anatomy of woody plants, Chicago 1917. 

 Lestiboudois, Th.: Phyllotaxie anatomique ou recherches sur les causes 



organiques des diverses distributions des feuilles; Ann. des scienc. nat. 



III Série, 1848, T. 10. 

 Nägeli, C. v.: Das Wachsthum des Stammes und der Wurzel bei den Ge- 



fässpflanzen und die Anordnung der Gefässstränge im Stengel, Bei- 

 träge zur wissensch. Botanik, Heft 1, 1858. 



Botanisk Tidsskrift. 37. Bd. \Q 



