2o6 



ROOTS OF WATER PLANTS 



[CH. 



pression, " elles grimpent en bas." He adds that Potamogeton 

 densus (Fig. 137 (7 and H) shows the same peculiarity. A more 

 recent writer^ has recorded that, when the turions of Pota- 

 mogeton obtusifolius germinate, they produce spirally coiled roots, 

 which apparently serve to anchor the plantlets in the mud. 



Twining roots are not confined to water plants; a case is 

 recorded by Darwin^, on the authority of Fritz Mtiller, in 



Fig. 137. T^imxig roots oi Zannichelliapalustris,!^. {A-F) and of Potamogeton 

 densus, L. (G, H). [Hochreutiner, G (1896).] 



which the aerial roots of an epiphytic Philodendron in the forests 

 of S. Brazil, twined spirally downwards round the trunks of 

 gigantic trees. That root tendrils merely represent a further 

 development of the general tendency to nutation common to 

 stems and roots, is indicated by C. and F. Darwin's^ record 



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

 {1908, etc.). 2 Darwin, C. (1891). ^ Darwin, C. and F. (1880). 



