. A textbook of botany for colleges and universities ... Botany. SAPROPHYTISM AND SYMBIOSIS 771 fests deciduous trees also appears to be distinct from the forms that parasitize the conifers. Even plurivorous species of Cuscuta grow very differently on different hosts, the number of forms on which they flower and fruit being much less than the number on which they can develop vegetative organs. Haustorial structures. — The haustoria of parasitic seed plants are much more complex than are those of the fungi, involving various elements in the cortical and vascular tissues. The simplest haustoria
. A textbook of botany for colleges and universities ... Botany. SAPROPHYTISM AND SYMBIOSIS 771 fests deciduous trees also appears to be distinct from the forms that parasitize the conifers. Even plurivorous species of Cuscuta grow very differently on different hosts, the number of forms on which they flower and fruit being much less than the number on which they can develop vegetative organs. Haustorial structures. — The haustoria of parasitic seed plants are much more complex than are those of the fungi, involving various elements in the cortical and vascular tissues. The simplest haustoria occur in such partial parasites as the Euphrasieae, where contact with the host often seems more or less casual. In the mistletoe, also a partial. Fig. 1084. — The mistletoe, a partial (water) parasite: A, spiny honey-locust trees (Gleditsia triacanthos), many of whose limbs are infested with mistletoe {Phoradendron Jlavescens); B, a close view of a single mistletoe plant; Rome, Ind —Photographs supplied by Land. parasite, but more specialized, the haustoria are prominent organs which exhibit some structural complexity, their hadrome elements coming in close contact with similar elements in the host. Still more specialized are the haustoria of Cuscuta (&g. 1082) and of Orohanche, their terminal cells deploying in all directions, and coming into such close contact with the host cells that sometimes it is difficult to distinguish one from the other, though the frontier cells of the parasite commonly are richer in starch than are the adjoining cells of the host; particularly in Oro- hanche are the cortex, leptome, and hadrome of the haustorium in con- tact, respectively, with the cortex, leptome, and hadrome of the host. Perhaps the acme of specialization is seen in Pilostyles, where the haustorial elements permeate the host tissues like fungal Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabil
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