Pentoxylon Stem

Pentoxylon Stem:-

> Pentoxylon sahnii and Nipanioxylon guptai are the stem genera of “Pentoxyleae”. The stems of Pentoxylon sahnii attained a diameter from 3mm to 2 cm. The stem has always been reported in association with the leaves called Nipaniophyllum.

> Presence of five steles in a cross- section of the stem has been the main reason for giving the name Pentoxylon to the genus. Many short lateral shoots or dwarf shoots were also present on the stem.

> Five steles occupied greater part of the stem in a cross-section. Each stele had its own cambium. The cambium was uniformly active in the young stems, but at maturity more secondary tissue developed towards the centre, and thus the secondary wood appeared eccentric.

> Primary phloem and primary xylem were present towards outer and inner sides of the cambium, respectively. Six steles have also been observed by Sahni (1948), although rarely. According to Vishnu-Mittre (1953) the number of steles varied along the length of the stem.

> There were present five much smaller bundles just alternating with the main bundles of the stem i.e. five steles. Each such bundle had a large amount of secondary wood. These were probably the leaf trace bundles.

> Medullary rays of the main steles were uniseriate, and they lacked ray tracheids, wood parenchyma and resin canals. The secondary wood resembled greatly with that of Araucaria. Uniseriate or bi-seriate bordered pits were present on the radial wall of tracheids.