MORPHOLOGY OF THE ROOT. 



37 



they may be likewise rooted in the soil, and receive from it 

 materials of their food. Having green foliage, they are capable 

 of elaborating such food, whether taken directly from the soil or 

 from the crude sap of the foster plant. The Mistletoes (Viscum 

 and its allies) are the principal examples of complete green 

 parasitic plants. Seeds dropped by birds on the boughs of trees 

 germinate there ; the root- end of the cauliclc points thither instead 

 of towards the earth ; the root, or what w r ould be such, pene- 

 trates the bark and in- 

 corporates itself with the 

 sap-wood so perfectly 

 that the junction of par- 

 asite with foster trunk 

 is like that of branch 

 with parent trunk. The 

 parasite is probably fed 

 by both elaborated and 

 crude sap, that is, both 

 by what the foster tree 

 has assimilated and 

 what it has merely taken 

 from the soil and air : 

 the former it can at once 

 incorporate ; the latter 

 it has first to assimilate 

 in its own green leaves. 

 Sometimes one Mistleto 

 is parasitic upon an- 

 other of the same or of 

 a different species. 



63. Partially parasitic plants (mostly green) may be either woody 

 and arborescent or herbaceous. The species of Clusia in tropical 



FIG. 74. Native epiphytes of Georgia. &c. : the erect one at the right an OrchH, 

 Epidendrum eonopseum ; the hanging one Tillandsia usneoides, called Long Moss. 



FIG. 75- Roots of Gerardia flava: some of the rootlets attaching themselves para- 

 Bitically to the root of a Blueberry. (From a drawing by Mr. J. Stauffer.) 



