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THE ROOT 161 
placed in moist sand; roots arising from stems of climbing plants 
or from stem cuttings. 
4. Prop roots or brace roots are such as grow out of the stem a 
short distance above the soil 
and extend diagonally into the 
ground, serving as supports to 
the stem. Examples: Indian 
Corn and Pandanus. 
5. Epiphytic roots are the 
roots of epiphytes or air-plants, 
many of which are common 
to tropical forests. In some 
instances, as in Vanilla and 
other epiphytic Orchids, these 
roots, arising from aerial stems, 
hang down free in the air and 
absorb water from rain by 
means of their several layered 
epidermis called a velamen. In 
others, as in the English Ivy, 
several short roots grow out of 
the stem at various intervals 
and adhere by their tips to 
walls, thus serving as supports 
for climbing. 
The Banyan (Ficus religiosa) 
of India can extend itself over 
large areas by means of its aerial ‘ 
roots. ‘These extend down ver- Fic. 95.—Vanilla planifolia, an epi- 
tically from horizontal branches phyte, growing on a tree in Jamaica, 
aiid formtee nks, upon anchor- 2 ; (Gager, after Maxon, U. S. Dept. 
ing themselves in the soil. 
6. ‘The roots of parasitic plants are known as Haustoria. These 
penetrate the bark of plants upon which they find lodgment, 
known as hosts, and absorb nutritious juices from them. The 
Mistletoe, Dodder and Gerardia are typical parasitic higher plants. 
CLASSIFICATION OF Roots As TO ForM.—Fusiform, or Spindle- 
shaped, like that of the radish or parsnip. 
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