At maturity they have inclined end cell walls with small pores and degenerate nuclei. The conduction cells of mosses, leptoids and hydroids, appear similar to those of fossil protracheophytes.
As they mature, the cells of these organisms have thickened walls with tiny pores and their nuclei become less active.  The conduction cells of mosses, leptoids, and hydroids share a similar structure to those found in ancient plant-like fossils called protracheophytes.