PARASITIC PLANTS. 



89 



tree where it happens to fall, and its nascent root, or rather the 

 woody mass that it produces in place of the root, penetrates the 

 bark of the foster stem, and forms as close a junction with its young 

 wood as that of a natural branch. The Cursed Fig, commonly be- 

 ginning as a i^arasite, sends down aerial roots, some of Avhich strike 

 into the wood of the foster tree lower down, while others descend 

 to the ground and draw from it a portion of their sustenance in the 

 ordinary manner. Some common herbaceous plants, hitherto not 

 suspected of such habits, have recently been found to fix themselves 

 clandestinely, under ground, by means of some of their rootlets, to 

 the roots of neighboring plants, and furtively draw from them a 

 portion of their sustenance. This is the case with our Comandra, 

 as well as with the Thesiums of the Old World, and also with our 

 Gerardias and many other plants of that family, which have long 

 been known as uncultivable, although the cause of their being so 

 has only lately been detected. It would appear that this partial 

 parasitism is necessary to their existence. Gerardia appears to im- 

 plant its rootlets upon the bark of the roots of neighboring slirubs, 

 and therefore to steal elaborated sap (Fig. 145, 14G). 



152. Pah or Colored Parasites, such as Beech-Drops, Pine-Sap, 

 &c., are those which are destitute of 

 green herbage, and are usually of a 

 white, tawny, or reddish hue ; in fact, 

 of any color except green. These 

 strike their roots, or sucker-shaped 

 discs, into the bark, mostly that of 

 the root, of other plants, and thence 

 draw their food from the sap already 

 elaborated. They have accordingly 

 no occasion for digestive organs of 

 their own, i. e. for green foliage. 

 The Dodder (Fig. 147) is a common 

 plant of this kind which is parasitic 

 above ground. Its seeds germinate 

 in the earth ; but when the slender 

 twining stem reaches the surrounding 



FIG. 147. The common Dodder of the Northern States (Cuscuta Gronovii), of the natural 

 size, parasitic upon the stem of an herb : the uncoiled portion at the lower end shows the 

 mode of its attachment. 148. The coiled embryo taken from the seed, moderately magnified. 

 149. The same in germination ; the lower end elongating into a root, the upper into a thread- 

 like leafless stem. 



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