PHYSIOLOGY. 391" 
brush, upon the stigma of several flowers, and he 
vot perfectly formed fruit, which again gave him 
new plants. In many other cases this has been 
done, which the limits of this work will not permit 
us to mention. Might it not be adviseable for gar- 
deners, who wish to have cherry-trees or other fruit- 
trees bear very early in the season, when they often 
get little or no fruit at all, to place a bee-hive 
with bees in the hot-house, and at the same time, to 
take care to let these busy insects get at as many 
flowers as possible ? 
§ 290. 
_ Nature seems to have given so very high a de- 
gree of irritability to some plants, merely to pro- 
mote the business of generation. Berberis vulgaris 
has very irritable stamens, for if they are bent only 
a little, they instantly rebound back to the pistil. Dr 
Smith, however, found that a few parts in them 
only are possessed of this irritability. Cactus tuna 
has likewise a great deal of irritability in its sta- 
mens. If they are touched with a quill, they all 
incline over the pistil. As soon, therefore, as in- 
sects touch these irritable spots in those plants, the 
irritability exerts itself, and impregnation takes 
place. Many more plants have these kinds of sta- 
mens, for imstance the whole family of Ascle- 
pias, Sc. 
The. elasticity of some stamens certainly alone 
favours impregnation in some plants, for instance, 
in Lopezia; Urtica; Parietaria ; Medicago ; Kalmia 5 
and others. | | 
x The 
