The leptoid of a Pteridophyte (fig.
Each leptoid is an elongated living cell with nucleus and a thin layer of protoplasm lining the wall (fig.
R, Optical section of leptoid (sieve-tube segment) of Phanerogam, with two proteid (companion) cells.
The end of the cell is slightly swollen, fitting on to the similar swollen end of the next leptoid of the row exactly after the fashion of a trumpet-hypha.
It is known as leptom, each constituent cell being a leptoid (fig.