. A textbook of botany for colleges and universities ... Botany. species that forms galls on legume roots (p. 787), also lives saprophyti- cally in the soil, and thus is a facultative form. The mildews, rusts, and smuts are representative parasitic fungi, most of which are deleterious to their host plants (fig. 180), some species producing conspicuous galls in various organs. Some of the Poly- poraceae (as the bracket fungi) are harmful parasites on trees. The hyphae of parasitic fungi are thought to be more specialized than are those of saprophytic forms, hav- ing greater power of pene- trati
. A textbook of botany for colleges and universities ... Botany. species that forms galls on legume roots (p. 787), also lives saprophyti- cally in the soil, and thus is a facultative form. The mildews, rusts, and smuts are representative parasitic fungi, most of which are deleterious to their host plants (fig. 180), some species producing conspicuous galls in various organs. Some of the Poly- poraceae (as the bracket fungi) are harmful parasites on trees. The hyphae of parasitic fungi are thought to be more specialized than are those of saprophytic forms, hav- ing greater power of pene- tration into woody and mechanical tissues, and it is likely also that their absorptive efficiency is greater. The penetrative power of the hyphae is due in large part to the substances which they se- crete, particularly various enzyms, such as the wood- destrovine enzvms of the Figs. 1079, of parasitic fungi: / , I , 1079, a hyphal filament of Albugo Candida from whicli tree-inhabiting fungi. ,here originate small spherical liaustoria that pene- Wounds of various kinds 'rate the parenchyma cells of the host plant, Lepi- tl i Tt t tVi â dium sativum i ro8o, a hyphal filament of PeroHOi/xira "^ -^ calotheca from which there origmate richly branch- sion of plant organs by ing haustoria that penetrate all parts of the paren- parasiteS. While ordinary ]hot the host plant, Asperula odorata; both 11 f. ⢠J figures highly magnified. â From DeBary. hyphae often invade the ^ s j & living host cells, in many cases they creep along the outer surface (as in various mildews) or penetrate between the cells, special branches known as haustoria piercing the walls (especially through the pits) and absorbing the contents of the lumina; surface forms are known as ectoparasites, while internal forms are termed endoparasites. In Albugo the haustoria are knoblike processes (figs. 1079, 158) and in Peronospora the hausto- rial branch may divide into a number of fin
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