218 MR. F. DARWIN ON THE CONNECTION 
formed by the continued propagation by tubers, as in various 
places large breadths have been seen, the flowers of the potatoes 
being all similarly affected. 
DESCRIPTION OF PLATE XXXIII. 
Sketches from nature, illustrating the malformation in Digitalis purpurea. 
Fig. 1. Terminal portion of the inflorescence. 
2. Anterior side of a corolla, with stamens. 
9. Posterior side of the same. 
4. Lateral view of the same. 
5. Entire flower, shown on its posterior side. 
6. The same, viewed laterally. 
Sketches showing malformation in the Potato. 
7. Flower of Potato, with staminiferous corolla, 
8. Normal stamen of same. 
9, 10, and 11. Staminiferous lobes of the corolla. 
On the Connection between Geotropism and Growth. 
By FRANCIS Darwin M.B., RR 
[Read April 6, 1882.] 
Ir the punctum vegetationis is removed from a root* by cutting 
off about 1:5 millim. by a transverse section, the root loses its 
power of bending geotropically, although it continues growing 
vigorously. This curious experiment was first made by Ciesielskit, 
and has been confirmed by my father and myself in a large number 
of observations{. Ciesielski made the further observation, that 
if a root be placed horizontally for a short time before the tip is 
cut off, the geotropic curvature will take place in spite of the 
operation. It must be understood that no curvature takes place 
during the period which elapses before the operation; conse- 
quently the fact of the curvature taking place afterwards, shows 
that the operation does not interfere with the act of curvature. 
These experiments we have also confirmed in various ways. 
It would be possible to draw two distinct conclusions from 
these experiments :—(1) It may be supposed that the operation 
of cutting off the tip acts as a shock, and so disturbs the organi- 
* E.g.of Vicia faba, Pea, or Phaseolus. 
t ‘Abwartskriimmung der Wurzel’ Inaug Dissert., Breslau, 1871. 
1 ‘The Power of Movement in Plants,’ ch. xi. 
