38 



LECTURE III. 



Rhinanihus, green-leaved plants which are parasitic only by-the-^^■ay, and fasten 

 themselves to the roots of neighbouring plants by some of their root-fibres. We 

 find the last stage in the reduction of the root-formation in phanerogamous para- 

 sites, finally, in the BalanophorecB and Rafflesiacece, in which, as has been mentioned 

 before, the vegetative body, seen apart from the flower-shoots, no longer allows 

 the differentiation into shoot and root to be recognised. In the Rafflesiacea the root 

 presents amorphous masses of cells, which become extended in the tissue of the host, 

 and in the BalanophorecB their parasitism brings about out-growths of tissue on the 



v^-«a; 



Fig. 17. — A Longitudinal section of the flower 

 of Brugntansia Zippclii, the vegetative body of 

 which is parasitic in the root (7c) of a Cissus. yovary, 

 represented in transveriie section at B (nat. size, 

 after Solms-Laubach), 



Fig. i%.—Balaiiophora fnngosa. lu root of host plant, 

 out of which the tuberous part of the parasite grows ; the 

 woody bundles of the host-root {represented as dark streaks) 

 penetrate into tlie latter; a, b, c young inflorescences (nat. 

 size). 



affected roots of the host-plant, which make the union of the parasite with this 

 yet closer, and call to mind in many respects the gall-formations produced by 

 insects (cf. Figs. 17 and 18). 



From what has been said concerning parasites, it follows that the typical roots 

 of vascular plants may lose their external form and anatomical structure completely, 

 under certain circumstances, so that their chief physiological properties alone are 

 maintained. 



If we now. turn to the more simply organised plants, to the Mosses and Algse, 



