In this article we will discuss about the anatomy of ephedra with the help of a suitable diagram.
The stem in its outline is wavy due to the presence of ridges and furrows (Fig. 17.2A). The epidermal cells are highly cuticularized, save for regions of furrow which have sunken stomata within a stomatal cavity (Fig. 17.2C). Below the ridge is the hypodermis of elongated fibres which provide mechanical support. The outer cortex is a single layer of chlorophyllous elongated palisade cells. Endodermis delimits the cortex from vascular elements.
As for the number and nature of vascular elements there are variable accounts. An internode in Ephedra consists of 8-12 collateral bundles, an alternate pairs of large and small ones. In E. foliata under each ridge there are five vascular bundles so that in a 3-ridged shoot there are 15 vascular bundles.
Thus, the stele is ectophloic dictyostele. This is in contrast to eustele. In E. virdis, there are eight vascular bundles, of which four are leaf traces and four are axial bundles. Leaf traces are smaller than axial bundles.
Secondary growth is due to the intrafascicular cambium present in vascular bundles, and joining with interfascicular cambium, this ring of the cambium cuts off the secondary xylem towards the inside and secondary phloem towards the outside.
Vessels are the most prominent feature of the Ephedra stem (Fig. 17.2B, D). In E. virdis are described tracheids and vessels whereas in the same species secondary xylem is described to comprise only tracheids.
Annual growth rings are seen with each year’s secondary growth. In several species of Ephedra from old world there are reports of occasional growth rings without vessels and also in E. equisetina the first year’s wood was entirely without vessels.