CH. xvi] TENDRIL ROOTS 205 



system of shrouds and stays to support the stem like a mast in 

 an erect position, while the pressure on the soft mud is lessened 

 by the buoyancy of the hollow internodes." 



There are other cases, again, in which anchorage depends on 

 some modification of the adventitious roots. Brasenia Schreberi 

 (peltata) 1 , for instance, is fixed by its well-developed root-caps, 

 which are of the nature of anchors, and prevent dislodgment 

 of the buoyant plant, when it is swayed about by the agitation 

 of the water surface. A still more remarkable method is the 

 production of spirally twisted roots, which in some cases fully 

 deserve the name of tendrils. Most of the known examples 

 occur in the Potamogetonaceae, but they have also been 

 recorded in the Hydrocharitaceae (Hydrilla)*, Fig. 136, and 



FIG. 136. Hydrilla verticillata, Presl. Tendril roots. [Kirchner, O von, Loew, E. 

 and Schroter. C. (1908, etc.).] 



Gentianaceae (Menyanthes)*, while the present writer has 

 noticed them in Myriophyllum verticillatum (Haloragaceae). 

 The first case among the Potamogetonaceae in which spirally 

 twisted roots were observed, seems to have been Cymodocea 

 antarctica 4 . At a later date the corkscrew roots of Zannichellia 

 palustris were fully discussed by Hochreutiner 5 (Fig. 137 AF, 

 p. 206). He describes these roots as long, unbranched, and 

 twining about other objects like tendrils to use his own ex- 



iSchrenk,J. (1888). 



2 Graebner, P., in Kirchner, O. von, Loew, E., and Schroter, C. 

 (1908, etc.). 8 Irmisch, T. (1861). 



4 Tepper, J. G. O. (1882). 5 Hochreutiner, G. (1896). 



