spiral vessels which extend for only a short distance up them, with no
line of demarcation between what is plainly the prolongation of the
leaf and the pedicel of a glandular hair. Therefore there would be
nothing anomalous or unusual in the basal parts of these tentacles,
which correspond with the marginal ones of Drosera, acquiring the power
of movement; and we know that in Drosera it is only the lower part
which becomes inflected. But in order to understand how in this latter
genus not only the marginal but all the inner tentacles have become
capable of movement, we must further assume, either that through the
principle of correlated development this
* Sachs, Traite de Botanique 3rd edit. 1874, p. 1026.
** Dr. Warming Sur la Diffrence entres les Trichomes, Copenhague,
1873, p. 6. Extrait des Videnskabelige Meddelelser de la Soc. d Hist.
nat. de Copenhague, Nos. 10-12, 1872. [page 360]
power was transferred to the basal parts of the hairs, or that the
surface of the leaf has been prolonged upwards at numerous points, so
as to unite with the hairs, thus forming the bases of the inner
tentacles.
The above named three genera, namely Drosophyllum, Roridula, and
Byblis, which appear to have retained a primordial condition, still
bear glandular hairs on both surfaces of their leaves; but those on the
lower surface have since disappeared in the more highly developed
genera, with the partial exception of one species, Drosera binata. The
small sessile glands have also disappeared in some of the genera, being
replaced in Roridula by hairs, and in most species of Drosera by
absorbent papillae. Drosera binata, with its linear and bifurcating
leaves, is in an intermediate condition. It still bears some sessile
glands on both surfaces of the leaves, and on the lower surface a few
irregularly placed tentacles, which are incapable of movement. A
further slight change would convert the linear leaves of this latter
species into the oblong leaves of Drosera anglica, and these might
easily pass into orbicular ones with footstalks, like those of Drosera
rotundifolia. The footstalks of this latter species bear multicellular
hairs, which we have good reason to believe represent aborted
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