A leptoid are elongated food-conducting cells in some moss

Moss

Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...

es. They are surrounded by strands of hydroids. They have some structural and developmental similarities to the sieve elements of seedless vascular plants. At maturity they have inclined cell walls with small pores with degenerate nuclei. The conduction cells of mosses are Leptoids and hydroids appear similar to those of fossil protracheophytes. Because of this, they may represent an intermediate stage in the evolution of plants.