THE PLANT AND ITS ENVIRONMENT 13 
when a sufficient supply is not available from the ground. 
Plants, such as aquatics, which can grow only under very wet 
conditions are hydrophytes. Most plants are not specialized to 
grow in either very dry or very wet habitats, but thrive under 
conditions intermediate between these two extremes (Tig. 6). 
Such plants are mesophytes and include the great majority of 
cultivated plants, such as beans, tomatoes, corn, squashes, etc. 

Fic. 8. Two species of tropical mistletoe which are hemiparasites 
Left, Viscum orientale, the root of which forms a single haustorium (absorbing 
organ). Right, Loranthus philippensis, the roots of which grow on the surface of 
the host and send many haustoria into it 
Parasites and saprophytes. While most plants manufacture 
their own food, there are many which live on food that has 
already been elaborated. Those plants that send absorbing organs 
into living plants from which they draw their nourishment are 
parasites. As true parasites do not contain chlorophyll with 
which to manufacture the food they require, they do not have the 
green color of chlorophyll (Figs. 7, 161,170). Some plants, how- 
ever, have absorbing organs by means of which they obtain mate- 
rials from other plants, and at the same time possess chlorophyll 
which enables them to manufacture food. Such plants are hem- 
parasites, of which the mistletoe is a good example (Fig. 8). 
