VITAL FORCE, INSTINCT, AND SENSATION. 53 
in search of the best place to settle in, and in every pollen-tube as it grows 
down through the entrance to an ovary and applies itself to one definite spot of 
an ovule, never failing in its object. The water-crowfoot, in deep water, fashions 
its leaves with finely divided tips, large air-passages, and no stomata; whilst, 
growing above the surface of the water, its leaves have broad lobes, contracted 
intercellular spaces and numerous stomata. Linaria Cymbalaria (see fig. 11) 
raises its flower-stalks from the stone wall over which it creeps towards the light, 
but as soon as fertilization has taken place, these same stalks, in that very place 
and amidst unchanged external conditions, curve in the opposite direction, so as 
Fig. 11.—Linaria Cymbalaria dropping its Seeds into Clefts in the Rocks. 
to deposit their seeds in a dark erevice, The flower-stalk of Vallisneria twists 
itself tightly into a screw and draws the flowers, which previously it had borne 
upon the surface of the water, down to the bottom when their stigmas have been 
covered with pollen-dust at the surface. These are all cases of unconscious action 
for a definite object, that is to say, they are the result of instinct. 
If, however, we attribute instinct to living plants, it is but a step further to 
consider them as endowed with sensation also. Feeling in animals is the con- 
comitant of a condition of disturbance in nerves and brain caused by a stimulus, 
which acts on the organs of sense, and is conveyed by nerves to the central 
organ. The transmission of the stimulus and the excited state of the brain and 
nerves are only molecular movements of the nervous substance, or, let us say, of 
the protoplasm, for nerve-fibres and nerve-cells are simply protoplasm developed 
in a particular manner. But 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 protoplasm, 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, for the cell-nucleus is to all appearance 
