Internal structure of Cycas:
Primary root structure: In a T.S. of young root. The following structures are seen. The outermost layer is epidermis or epiblema. It has unicellular root hair on it. Next is a thick cortex made up of parenchymatous cells. Innermost layer of cortex is endodermis followed by a single layer pericycle. xyluim is diarch and exarch. Alternating with the protoxylem bundles are two phloem bundles. A pith may or may not be present in the centre.
Secondary growth in the root: There is no cambium in the primary structure of root. mbium arises outside the protoxylem and inside the phloem. It is a zigzag ring in the beginning. It cuts of secondary xylem on its inner side and secondary phloem on its outer side, soon this ring becomes circular, The same ring remains active throughout the life unlike in the stem. Even after the formation of secondary xylem, primary xylem remains intact Primary phloem is however crushed and not seen in a nature root.
