Insectivorous Plants · Charles Darwin
BYBLIS.
The limpid contents of the glands of Pelargonium zonale became cloudy and granular in from 3 m. to 5 m. when they were immersed in a weak solution of the carbonate of ammonia; and in the course of 1 hr. granules appeared in the upper cells of the pedicels. As the aggregated masses slowly changed their forms, and as they suffered disintegration when left for a considerable time in a strong solution, there can be little doubt that they consisted of protoplasm. It is doubtful whether an infusion of raw meat produced any effect. The glandular hairs of ordinary plants have generally been considered by physiologists to serve only as secreting or excreting organs, but we now know that they have the power, at least in some cases, of absorbing both a solution and the vapour of ammonia. As rain-water contains a small percentage of ammonia, and the atmosphere a minute quantity of the carbonate, this [page 355] power can hardly fail to be beneficial. Nor can the benefit be quite so insignificant as it might at first be thought, for a moderately fine plant of Primula sinensis bears the astonishing number of above two millions and a half of glandular hairs,* all of which are able to absorb ammonia brought to them by the rain. It is moreover probable that the glands of some of the above named plants obtain animal matter from the insects which are occasionally entangled by the viscid secretion.
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