circular hollow between the infolded apex and infolded prominence
apparently contracts into the narrow orifice, wherein the valve and
collar will be developed; the bladder itself being formed by the
confluence of the opposed [page 427] margins of the rest of the leaf.
But strong objections may be urged against this view, for we must in
this case suppose that the valve and collar are developed
asymmetrically from the sides of the apex and prominence. Moreover, the
bundles of vascular tissue have to be formed in lines quite
irrespective of the original form of the leaf. Until gradations can be
shown to exist between this the earliest state and a young yet perfect
bladder, the case must be left doubtful.
As the quadrifid and bifid processes offer one of the greatest
peculiarities in the genus, I carefully observed their development in
Utricularia neglecta. In bladders about 1/100 of an inch in diameter,
the inner surface is studded with papillae, rising from small cells at
the junctions of the larger ones. These papillae consist of a delicate
conical protuberance, which narrows into a very short footstalk,
surmounted by two minute cells. They thus occupy the same relative
position, and closely resemble, except in being smaller and rather more
prominent, the papillae on the outside of the bladders, and on the
surfaces of the leaves. The two terminal cells of the papillae first
become much elongated in a line parallel to the inner surface of the
bladder. Next, each is divided by a longitudinal partition. Soon the
two half-cells thus formed separate from one another; and we now have
four cells or an incipient quadrifid process. As there is not space for
the two new cells to increase in breadth in their original plane, the
one slides partly under the other. Their manner of growth now changes,
and their outer sides, instead of their apices, continue to grow. The
two lower cells, which have slid partly beneath the two upper ones,
form the longer and more upright pair of processes; whilst the two
upper cells form the shorter [page 428] and more horizontal pair; the
four together forming a perfect quadrifid. A trace of the primary
division between the two cells on the summits of the papillae can still
be seen between the bases of the longer processes. The development of
the quadrifids is very liable to be arrested. I have seen a bladder
1/50 of an inch in length including only primordial papillae; and
another bladder, about half its full size, with the quadrifids in an
early stage of development.
364