THE MOVEMENTS OF PLANTS. 
i 
203 
concluded that when seedlings are freely exposed to a lateral 
light, some influence is transmitted from the upper to the 
lower part, causing the latter to bend. 
Flowers. — There are many instances of the various parts of 
flowers moving under the influence of stimuli ; hut the imme- 
diate causes in the different cases have not been so thoroughly 
investigated as by Mr. Darwin in the case of the vege- 
tative organs, and at present, therefore, but little can be said 
beyond the fact that they do move. Thus, commencing with 
bracts, it may easily be seen how the erect bracts of the 
involucre of the dandelion become reflexed as soon as the fruit 
is ripened, thus allowing the parachute-like achenes to escape 
easily. Moving corollas are very numerous. A large series of 
plants might be mentioned of which the corollas close up, either 
as soon as the sun is obscured, as Mesembryanthemum, Anagallis 
arvensis, Convolvulus , &c., or else at evening, such as many 
Compositse, including the Daisy and Dandelion, re-expanding 
on the return of light. Conversely, some night-flowering 
plants unfurl their petals only at night, coiling them up by 
day. As an illustration Silene nutans may be taken, concern- 
ing which Dr. Kerner tells us * that a flower lasts three days 
and three nights ; with the approach of dusk the bifid limbs of 
the petals spread out with a flat surface, and fall back upon the 
calyx. In this position they remain through the night ; curl- 
ing themselves up into an incurved spire and becoming 
longitudinally creased at the same time, on the return of 
sunlight and a warm temperature. Ho sooner does evening 
return, than the wrinkles disappear, the petals become smooth, 
uncurl themselves, and falling back against the calyx, the 
corolla is again expanded (PL Y. figs. 17, 18). 
In the Pea family, or Leguminosse, there are several 
instances of the corolla having a power to move when irritated. 
Thus in the genera Genista and Indigo , the claws of the petals 
act like springs kept in a state of tension ; for when the corolla 
is touched, as by an insect in search of honey, the claws sud- 
denly curl downwards, and the petals consequently drop 
vertically, while the stamens, previously concealed within the 
keel petals, are violently thrown upwards, showering* the bee 
with pollen, f 
The movement of stamens is perhaps more curious, and 
apparently intimately connected with the phenomenon of insect 
fertilization. As an example of slow movement, Parnassia 
palustris may be mentioned. In this flower, each stamen in 
succession rises up, places the anther on the stigma, and having 
shed its pollen, retires and falls back upon the petals. Each 
* Flowers and their Unbidden Guests, p. 132. 
t Journ. of Linn. Soc. vol. ix. p. 355, and vol. x, p. 468. 
