THE NUTRITION OF PLANTS 157 
119. Saprophytes. In the case of saprophytes dead bodies 
or body products are attacked, and sooner or later all or- 
ganic matter is attacked and decomposed by them. The de- 
composition is a result of the nutritive processes of plants 
without chlorophyll, and were it not for them " the whole sur- 
face of the earth would be covered with a thick deposit of 
the animal and plant remains of the past thousands of years." 
The green plants, therefore, are the manufacturers of or- 
ganic material, producing far more than they can use, while 
the plants without chlorophyll are the destroyers of organic 
material. The chief destroyers are the Bacteria and ordi- 
nary Fungi, but some of the higher plants have also adopt- 
ed this method of obtaining food. Many ordinary green 
plants have the saprophytic habit of absorbing organic ma- 
terial from rich humus soil ; and many orchids and heaths 
are parasitic, attaching their subterranean parts to those of 
other plants, becoming what are called " root parasites." 
120. Parasites. Certain plants without chlorophyll are 
not content to obtain organic material from dead bodies, 
but attack living ones. As in the case of saprophytes, the 
vast majority of plants which have formed this habit are 
Bacteria and ordinary Fungi. Parasites are not only modi- 
fied in structure in consequence of the absence of chloro- 
phyll, but they have developed means of penetrating their 
hosts. Many of them have also cultivated a very selective 
habit, restricting themselves to certain plants or animals, 
or even to certain organs. 
The parasitic habit has also been developed by some of 
the higher plants, sometimes completely, sometimes par- 
tially. Dodder, for example, is completely parasitic at 
maturity (Fig. 148), while mistletoe is only partially so, 
doing chlorophyll work and also absorbing from the tree 
into which it has sent its haustoria. 
That saprophytism and parasitism are both habits grad- 
ually acquired is inferred from the number of green plants 
which have developed them more or less, as a supplement to 
