176 
PARASITES 
in the intermediate zone ; they are equally well adapted for 
this form of life. So also they become shore-plants. 
For further details see Part II., especially Polypodium, 
Platycerium, Bromeliaceae, Tillandsia, Araceae, Orchid- 
aceae, Vanilla, Oncidium, Bulbophyllum, Scuticaria, Phalae- 
nopsis, Clusia, Ficus, Marcgravia, Dischidia, Rhododendron, 
Myrmecodia. 
Parasites 1 . We may again divide plants according to 
their mode of nutrition into independent plants, which take 
in all their food as simple inorganic compounds, parasites, 
saprophytes, and insectivorous plants. Parasites draw the 
whole or part of their food-materials from other plants (their 
hosts) by means of special organs termed suckers or haustoria . 
They are very numerous among the Fungi, and there are 
many parasitic seed-plants, certain orders being entirely 
composed of them, e.g. Loranthaceae, Rafiflesiaceae, &c. 
In most of these cases the suckers are modified roots, 
developed from the parasite at points of close contact with 
the host. The sucker penetrates the tissues of the host plant 
and grows into organic union with them ; if the host grow in 
thickness, the suckers grow in length to keep pace with it. 
Some parasites are confined to one species of host, others 
are more general in their attacks. 
Parasites are classed as total or partial , according to 
whether they take all or some of their nourishment from 
the host. In the latter case they appear only to take raw 
materials — the water and other substances absorbed by the 
roots — and therefore require green tissue of their own. In 
the former case chlorophyll is rendered useless, and they 
possess none ; their leaves are reduced to a more or less 
rudimentary condition or even the whole shoot, as in Raf- 
flesiaceae, whose vegetative body is reduced to a mycelium 
like that of a fungus. The inflorescence of parasites, on the 
other hand, is comparatively little degraded in structure. 
The simplest form of partial parasitism occurs in the 
Rhinanthus group of Scrophulariaceae (^.z\), and in Thesium 
and some Santalaceae ; all are parasitic by their roots upon 
the roots of grasses, &c. Viscum and other Loranthaceae, 
Myzodendraceae, &c., are parasitic upon the stems of their 
hosts, and may be mistaken for epiphytes. 
1 Schimper, op . cit . ; Hemsley in Linn. Soc. Journ. XXXI. 
