SOME OBSERVATIONS ON THE PROBLEM OF VESSEL LENGTH DETERMINATION IN WOODY DICOTYLEDONS

Abstract

A NUMBER of general statements as to the length of vessels in dicotyledonous trees will be found in the literature, but analysis usually shows the experimental basis upon which they are founded to be somewhat meagre and uncertain. In the course of the studies on wood anatomy which have been in progress during the last few years in the Botany Department in Leeds, injection experiments with Indian ink suspensions have frequently given indications of considerable vessel lengths. The observations have also directed particular attention to the very marked difference in length which appears to exist between the vessels of ring and diffuse porous types of wood. Dr Bruno Huber (I935) has recently pointed out that the conclusion reached in Leeds that the vessel lengths are much greater in ring porous types is in good agreement with his own observations upon the greater velocity of movement of water in these types also; his conclusion is based upon his experiments on the speed of propagation along the wood of a higher temperature from a point of local application on the surface of the wood. In the Leeds work the tree types with great vessel lengths have been found to be ones in which the resumption of cambial activity spreads extremely rapidly down the tree once it has been initiated in the buds, and a causal connexion between these two phenomena has been suggested (Priestley et al. I933). Vhilst these injection experiments seem to place the great difference in vessel length between ring and diffuse porous types beyond all doubt, it was however noted in every case that the injection had apparently not reached the end of the vessel. So long as this is the case, there must remain some doubt as to the exact significance of this difference in the length of the injection, and the present report embodies the results of further investigations of the problem from two distinct angles.