INFLUENCE OF ENVIRONMENT 279 
case of such complete parasites as the dodder (Cuscuta) 
or the gigantic Rafflesia of Sumatra, the plants are quite 
destitute of chlorophyll and completely dependent upon 
the host for their nourishment. In these the leaves are 
reduced to scales, and the plant sends root-like suckers 
into the host, or, in the case of Rafflesia and some re- 
lated plants, the whole vegetative part of the parasite 
lives within the host, like a fungus, and only the 
monstrous flowers are borne upon the outside. 
Similar in appearance to these parasites are a number 
of saprophytic plants which get their nourishment 
mainly from the decaying organic matter in vegetable 
mouldorhumus. Both leaves and roots in these plants 
are imperfectly developed (Fig. 59, C), and in some 
cases, at least, in common with many other plants, they 
are intimately associated with a fungus in the soil 
which seems to supply them with the food elements 
derived from the organic matter in the earth. The 
curious Indian pipe (Monotropa) and its more showy 
relation, the crimson snow plant (Sarcodes) of the 
Sierra Nevada, are examples of these humus plants. 
In all these parasites and saprophytes there is a marked 
degeneration of the assimilating organs, and this often 
extends to other parts of the plant, including the ovules 
and embryo. 
SYMBIOSIS 
A curious association of two plants together, or less 
often of a plant and animal, is a not uncommon occur- 
rence, this “symbiosis” being apparently mutually 
beneficial, although sometimes it looks more like a case 
of parasitism. A number of liverworts, e.g. Blasia, 
