90 



THE ROOT, 



herbage, it forms suckers, which attach themselves firmly to the 

 surfoce of the supporting plant, penetrate its epidermis, and feed 

 upon its juices ; while the original root and base of the stem perish, 

 and the plant has no longer any connection with the soil. Thus 

 stealing its nourishment ready prepared, it requires no proper diges- 

 tive organs of its own, and, consequently, does not produce leaves. 

 This economy is foreshadowed in the embryo of the Dodder, which 

 is a naked thread spirally coiled in the seed (Fig. 148, 149), and 

 presenting no vestige of cotyledons or seed-leaves. A species of Dod- 

 der infests and greatly injures flax in Europe, and sometimes makes 

 its appearance in our own flax-fields, having been introduced with 

 the imported seed. Such parasites do not live upon all plants in- 

 discriminately, but only upon those whose elaboi'ate juices furnish a 

 propitious nourishment. Some of them are restricted, or nearly so, 

 to a particular species ; others show little preference, or are found 

 indifferently upon several species of different families. Their seeds, 

 in some cases, it is said, will genninate only when in contact with 

 the stem or root of the species upon which they are destined to live. 

 Having no need of herbage, such plants may be reduced to a stalk 

 bearing a single flower (Fig. 965) or a cluster of flowers (Fig. 9G8), 

 or even to a single blossom developed from a bud directly parasitic 

 on the bark of the foster plant. Of this kind are the several species 

 of Pilostyles (parasitic flowers on the shoots of Leguminous plants) 

 in Tropical America, one species of which was recently discovered 

 by Mr. Thurber near the southern borders of New Mexico. Here 

 the flowers are small, only about a quarter of an inch in diameter. 

 The most wonderful plant of this kind is that vegetable Titan, the 

 Eafflesia Arnoldi of Sumatra (Fig. 150), which grows ujwn the 

 stem of a kind of Grape-vine. It is a parasitic flower, measuring 



FIG. 150. RafBesia Arnoldi ; an expanded flower, and a bud, directly parasitic on the stem 

 of a Tine : reduced to the scale of half an inch to a foot. 



