A study has been made, by light and electron microscopy, of the structure of the phloem tissue and sieve tubes of Sallx oaprsea. and the relevance of the findings to the electrokinetic theory of transport has been discussed. The anatomical features of the phloem at the cellular level do not seem particularly favourable to the theory; on the other hand, the ultra structure of the sieve tubes and in particular the prevalence of "slime" in this species and many other species being composed of banded fibrils, seems to favour the electro kinetic theory at least as much, as any other. A supporting calculation is given.