182 . EPINASTY. [CH. VII 



their upper surface may face upwards'. If a yew branch 

 bearing quite young buds is fixed in a horizontal position 

 with its lower surface upwards, the twisting of the leaves 

 takes place precisely as it does in a normal branch. Thus 

 the shoot, although from the arrangement of its leaves it 

 resembles a normal shoot, really developes with its 

 morphologically upper side downwards. In this respect 

 it differs from the shoots of the hazel, lime, etc. in which 

 an inverted shoot recovers its normal position by means 

 of torsion of the intemodes. The best way of fixing 

 the yew branch in its inverted position is not to twist 

 it on its axis but to bend over a horizontal branch 

 into a C form, until its free end is inverted but hori- 

 zontal; it can be fixed in this position by being tied in 

 two places to a stick fixed into the earth. The torsion 

 of the leaves requires several weeks for completion. 



(227) Epinasty\ 



This curvature (due to internal stimulus) may be 

 observed in a variety of plant-members. The strong 

 epinastic curvature of the leaves of Ranunculus ficaria 

 have been made use of in exp. 217, and similar curvatures 

 by which the leaves are pressed against the ground are to 

 be see'n in Plantago media, and in Pinguicula. 



(228) Gombmation of epiTiasty and geotropism\ 



The leaves of the dock (Rumex) serve for this 



^ See a good figure of Ahies pectinata in Frank's Lehrbuch der 

 Botanik, 1892, i. p. 475. 



2 H. de Vries in Sachs' Arbeiten, i. p. 252 ; see also Vines, AnnaU of 

 Botany, 1889. 



' H. de Vries in Sachs' Arbeiten, i. p. 255. 



