The layers appear to be made up of elements which are arranged radially.
In some hydroids the founder-polyp, developed from a planula after fixation, throws out numerous outgrowths from the base to form the hydrorhiza; these outgrowths may be radially arranged so as to form by contact or coalescence a flat plate.
In the Mosses the plant-body (gametophyte) is always separable into a radially organized, supporting and conducting axis (stem)
In Gymnosperms, where vessels and fibres are absent, the late summer wood is composed of radially narrow thick-walled tracheids, the wood of the succeeding spring being wide-celled and thin-walled, so that the limit of the years growth is very well marked.
In the latter event the cells of the primary rays are either merely stretched radially, or they divide to keep pace with the growth of the bundles.
