The key difference between hydroids and leptoids is that hydroids are specialized cells that conduct water in bryophytes and are analogous to tracheids in vascular plants, while leptoids are specialized cells that transport sugar in bryophytes and are analogous to sieve elements in vascular plants.
Bryophytes are a group of non-vascular plants. In fact, they are primitive plants that lack true stem, roots and leaves. They don’t have xylem or phloem. However, some mosses, mosses especially in the moss subclass Polytrichidae, have specialized cells to conduct water, minerals and sugar. Hydroids are specialized cells that transport water and minerals in some mosses. They are analogous to tracheids in vascular plants. Leptoids are another type of specialized cells that transport sugar and other nutrients in bryophytes. Moreover, they are analogous to sieve elements of vascular plants.
