'■> o 
XATVRE XOTES 
is easy, or, as a recent magazine article puts it, “ the state 
induced by the stimulation of protoplasm, which is what we call 
sensation, cannot be essentially different in vegetable protoplasm 
from what it is in animal, since the protoplasm itself, the physical 
basis of life in both plant and animal, is not different. In isolated 
plant-cells, indeed, it may amount to such a concentration of the 
condition of stimulation as to be called sensation ” ; and this is 
but a paraphrase of what Professor A. Kerner has advanced in 
his Natural History of Plants. 
This article, however, does not attempt to explain the 
phenomena, but simply to call attention to and enlist interest 
in them. Other explanations have been offered, such as vaguely- 
suggested electrical currents, and when we know more of this 
form of force it may be possible to detect it with some ultra- 
sensitive electroscope, but till then let it pass. A most interest- 
ing example of spontaneous movement is exhibited by the 
pollinia of many British orchids, first noticed by a Scotch 
gardener, David Brown, quoted at length by Darwin in his 
masterly work on the fertilisation of orchids. This may be seen 
by anyone, as the common spotted orchis of our hedgerows 
shows it very plainl}’. One of the distinguishing characters 
of an orchid flower is that the pollen is massed together into 
two compact bundles, either round or ovate, and these are called 
pollinia. These masses are connected, by thread-like stalks, with 
round or saddle-shaped bodies placed at the base of the lip, 
as the chief part of the corolla is called, and are only loosely 
adherent to the flower. It happens, therefore, that when an 
insect in search of honey alights on the conveniently-placed 
labellum (lip), and advances its head in order to reach the 
honey secreted by the nectary of the flower, the pollinia are 
ffislodged, and adhere to the insect’s head or to the back of its 
thorax, when it flies away to visit another flower of the same 
kind. But if the adhering pollinia retained their first posi- 
tion they would not strike the viscid stigmatic surface of the 
second flower, and Nature provides that the minute stalks in a 
few seconds bend over and assume the exact posture to effect 
the desired object of depositing the pollen where it is required. 
A simple way of observing this is to take an ordinary lead pencil 
and to insert the point over the base of the labellum into the 
nectary of the flower, which should be a freshly expanded one. 
On withdrawing the pencil the two minute grey-blue pollinia will 
be seen adhering to it in a position almost at right angles to its 
axis; but if they kept so when the insect visited the next flower 
the pollen-masses would fail to strike the stigma, and so it is pro- 
vided that in about five seconds the pedicels bend forward, and 
the pollinia assume the required place to exactly strike the 
stigmatic surface of the next flower the insect visits in search 
of honey. 
Other British orchids exhibit the same interesting phenomena, 
as quoted by Darwin, but the bee-simulating kind, Ophrys apifera. 
