in plants, unicellular or multicellular formations that serve to absorb various substances.

Haustoria in parasitic angiosperms (for example, in the dodder and the broomrape) are multicellular formations that are, for the most part, modified roots. They develop upon contact of the parasitic plant with the body of the host plant, taking root in the host’s tissue and absorbing nutritive substances from it. The haustoria of endosperms and of other structures of the embryonic sac in certain angiosperms are modified cells that serve to increase the intake of nutritive substances by the embryo from the surrounding tissues. In fungi the haustoria are outgrowths of the fungus cells that penetrate into the host’s cells.