An Undescribed Thermometric Movement of the 
Branches in Shrubs and Trees \ 
BY 
W. F. GANONG, Ph.D. 
Professor of Botany in Smith College. 
With six Figures in the Text. 
OME years ago I noticed an apparent radial movement of the ascending 
branches in certain shrubs and small trees, whereby the branches were 
brought closer to the main stem in the winter, quite independently of the 
leaf-fail, and were separated from it on the approach of spring. After trying 
in vain to find some account of this movement, and its causes, in the 
literature accessible to me 2 , and from various persons informed on such 
matters, I undertook a study of it, with results which follow. 
In the autumn of 1898 I chose six shrubs and small trees, in the Botanic 
Garden of Smith College, which showed the movement and which were 
isolated from other woody plants. Selecting long slender branches on the 
north, south, east, and west sides of each plant, I made near the top of 
each, and on the side radial to the plant, small dots with water-proof India 
ink, the approximate positions of which were marked for convenience by 
coloured threads. It was then possible, with the aid of an assistant, to 
1 Read before the Society for Plant Morphology and Physiology, at its Philadelphia Meeting, 
Dec. 29, 1903. 
2 I have found no direct references to this movement, although it seems unlikely that it could 
have escaped notice and description ; and the only other mention of it that I have been able to secure 
by inquiry is a statement in a letter that a resident of Washington, D.C., has noticed it in the lower 
branches of the Ginkgo. The inward movement of the branches after removal of the weight of the 
leaves in autumn is said to be known to nurserymen ; and some measurements of this movement in 
a shrub are given in a note by Agnes Frye in Nature , vol. lv, 1896, p. 198, and in a branch of horse 
chestnut, by Miller Christy in Journal of the Linnean Society, xxxiii, 1898, pp. 501—506. The 
works of Wiesner, Baranetsky, and others on the determinants of branch position appear not to touch 
this subject. Recently Mr. E. F. Bigelow, of Stamford, Conn., has written me that two correspon- 
.dents of his have asked him the causes of branch movements noticed by them ; in one case it was a 
spruce, whose branches rise in wet weather and fall in dry, and in the other it was a pine, whose dead 
lower branches rise in warm, and fall in cold weather. Apparently there is more in this subject than 
has hitherto been supposed. 
[Annals of Botany, Vol. XVIII. No. LXXII. October, 1904.] 
