LEAFLESS PARASITIC PLANTS. L]5 



its taste. Gum and Sugar, therefore, are to be considered as the 

 materials, out of which the Vegetable tissues are constructed ; 

 and Starch must be converted into one of these, before it can be 

 applied to a similar purpose. 



343. Now the proper juice elaborated by the leaves of one 

 plant, may sometimes serve for the nourishment of another. A 

 group of parasites, which, having leaves of theii own, can ela- 

 borate for themselves the crude sap they obtain from the roots 

 of another tree, has been already described (. 320) ; but there is 

 another, which is destitute of leaves as well as of roots, and 

 which is therefore dependent for support, on the elaborated sap 

 of the plants, to which its different kinds respectively attach 

 themselves. And as the nature of the proper juice of each spe- 

 cies varies much more, than does that of the crude sap, these 

 parasites cannot subsist upon the fluids of many different species, 

 but are for the most part restricted to those of a few. Most of 

 them grow upon the roots or underground stems of others ; no 

 part of them appearing above the surface (in general at least), 

 except the flower-stalks which are occasionally sent up. They 

 abstract the nutritious fluid from the plants to which they cling, 

 by means of a number of little suckers, which are formed upon 

 their roots, and which fix themselves to the bark of the stem 

 and roots ; and in this manner, they not unfrequently cause the 

 death of the plant, by drawing off its juices. 



344. One of the commonest kinds is the Orobanc/te. or 

 Broomrape, so named from the ravages it is thought to commit 

 on the Broom and Gorse of our heaths. The different species of 

 this plant infest different kinds of vegetables ; thus one infests 

 broom and furze ; and in many parts of Flanders, the farmers are 

 altogether deterred from the cultivation of clover by another 

 species, of which the seeds lie dormant in the soil, until it is 

 made to support plants upon which the parasite can grow, and 

 which it then attacks vigorously. Another species of this genus 

 confines itself to certain Composite flowers, as the Knapweed ; 

 one is found exclusively upon the roots of Hemp, and another 

 upon those of Ivy. The Cuscuta, or Dodder, is another plant of 

 the same description, which attaches itself to the sterns of the 



