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.
CONCLUDING REMARKS ON THE DROSERACE .
The six known genera composing this family have now been described in
relation to our present subject, as far as my means have permitted.
They all capture insects. This is effected by Drosophyllum, Roridula,
and Byblis, solely by the viscid fluid secreted from their glands; by
Drosera, through the same means, together with the movements of the
tentacles; by Dionaea and Aldrovanda, through the closing of the blades
of the leaf. In these two last genera rapid
* My son Francis counted the hairs on a space measured by means of a
micrometer, and found that there were 35,336 on a square inch of the
upper surface of a leaf, and 30,035 on the lower surface; that is, in
about the proportion of 100 on the upper to 85 on the lower surface. On
a square inch of both surfaces there were 65,371 hairs. A moderately
fine plant bearing twelve leaves (the larger ones being a little more
than 2 inches in diameter) was now selected, and the area of all the
leaves, together with their foot-stalks (the flower-stems not being
included), was found by a planimeter to be 39.285 square inches; so
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