52 INTRODUCTION TO BOTANY 
saprophytes have fungi growing upon their roots in such ways 
as to assist in securing food. These are called symbiotic sapro- 
phytes. The Indian pipe (Monotropa) often has these root 
fungi (mycorrhiza). 
Partial saprophytes, among flowering plants, are not easily 
recognized by their form and color, but may be known by their 
inability to flourish without considerable humus in the soil. 
52. Parasites. The dodders are the most familiar flower- 
ing parasites. One of the commonest species is abundant 
in the central and north- 
eastern states, its thread- 
like, golden-yellow stems 
forming great tangled 
masses on many kinds of 
plants, as clover, golden- 
rods, and willows, that 
grow in damp places. 
The dodders (fig. 84) and 
some root parasites, such 
as the beechdrops, squaw- 
z root, and cancer-root, are 
Fic. 35, Mistletoe growing upon a branch complete parasites and have 
ins Cady no green foliage. Other 
After Bonnier and Sablon : 
plants, such as the mistle- 
toe (fig. 35), have green leaves and do photosynthetic work, 
but depend on the host for water and the mineral substances 
dissolved in it. Such plants are called partial parasites. 
53. Damage inflicted by parasites. Many parasites take so 
much water and plant food from the host. that they may 
cause serious injury to cultivated plants and to forest trees. 
The flax dodder and the clover dodder often do great damage 
to crops in this country and in Europe, and another species ! 
ix sometimes troublesome in fields of alfalfa. In the south- 
western states the American mistletoe is so injurious to dicoty- 
ledonous trees that it is often necessary to cut it away from 
1 Cuscuta arvensis, 
