ROOTS AND THEIR USES 179 



200. Roots of Climbing Plants. — Among the means used 

 by climbing plants. to attach themselves to the objects upon 

 which they climb are various forms of adventive roots. Some 

 tropical plants support themselves by wrapping their roots 

 tightly about the trunks of trees. Some, like the vanilla, 

 form slender root-tendrils, that are much like branch- and 

 leaf-tendrils. The roots of a few climbing plants take 

 the form of spines. The trumpet creeper has much-branched 

 roots whose root hairs penetrate the fine crevices of the wall 

 or other supporting object and so obtain a firm hold. 



201. Roots of Parasitic Plants. — We have learned that 

 many of the simpler plants that are without chlorophyl — 

 such as the rusts and some of the bacteria — obtain their food 

 directly from living plants or animals, upon or in whose bodies 

 they live. They are parasites. The great majority of the 

 seed plants have chlorophyl and manufacture most or all of 

 their own food. But even among the seed plants there are 

 not a few which obtain at least part of their food ready made, 

 and so are saved the trouble of making it for themselves. 

 Some of these are saprophytes — that is, they feed upon 

 dead organic substances, usually mth the aid of fungi that 

 live in or upon their roots or stems. Others are parasitic 

 upon living plants. In plants whose habit of life is so unusual 

 we may expect to find marked peculiarities of structure. 

 These peculiarities appear largely in the roots, because it is 

 by means of roots that such a parasite takes its food from the 

 host. 



The seedling of a dodder (Fig. 112) has a primary root 

 which pushes into the soil, and a stem which grows in length 

 rather rapidly and which may remain alive, if it does not 

 become attached to a host plant, only so long as the supply 

 of food in the seed holds out. If the stem comes in contact 

 with a plant upon which it can live — which may, in the case 

 of different species of dodder, be a plant of clover, hop, flax, 

 or any one of a rather long list — it sends out small roots, or 



