On Epinasty and Hyponasty. 
BY 
SYDNEY H. VINES. 
With Woodcuts 7 and 8. 
HE analysis of the conditions which determine the 
1 position assumed by dorsiventral members in the 
course of their growth is a problem which, though it has 
engaged the attention of many observers, cannot as yet be 
regarded as completely solved. 
In giving a brief historical outline of these observations, 
noting the gradual growth of knowledge on the subject, the 
first which need be considered are those of Frank 1 . As the 
result of a long series of experiments he came to the con- 
clusion that dorsiventral members possess a peculiar form of 
irritability to the directive influence of light and of gravity, in 
virtue of which they place their flat surfaces perpendicularly to 
the direction of incidence of the rays of light or of the action 
of gravity, in such wise that the normally superior surface of 
the member is turned to the light, in the one case, and is 
uppermost in the other. To these phenomena Frank gave 
the names Transverse Heliotropism and Geotropism respec- 
tively, — names which are now commonly replaced by the less 
cumbrous terms Diaheliotropism and Diageotropism, suggested 
by Darwin. 
1 Frank: Die natiirliche wagerechte Richtung von Pflanzentheilen, etc., Leipzig, 
1870. For a full discussion of this subject see Vines, Lectures on the Physiology 
of Plants, Cambridge, 1886, Lectures 17 and 18. I purposely omit all reference 
to observations on the torsions of these members, as my own researches only refer 
to these incidentally. 
[Annals of Botany, Vol. III. No. XI. August, 1889. ] 
