A Study of 'Phloeotracheids' in Haustoria of Santalaceous Root Parasites using Scanning Electron Microscopy

Tracheary elements within haustoria of six santalaceous rootparasites have been examined by scanning electron microscopywith particular reference to those cells which contain granules.These cells have been called ‘phloeotracheids’ byearly workers. The granules lie free within the lumen of thecell from which a protoplast is absent at maturity. The granulesoccur in short vessel elements and in imperforate cells whichare thought to represent a specialized type of tracheid. Phloeotracheidsare confirmed in Exocarpus bidwilliiand Mida salicifolia andreported for the first time in Buckleya distichophylla, Comandraumbellata, Nestronia umbellataand Pyrularia pubera. The structureof phloeotracheids shown by scanning electron microscopy isdiscussed in relation to previous studies.