Medical Officers of the Army of India.
43
The process of gaseous evolution, in fact, plays the same part in the case of
Ottelia as is attained in Vallisneria by the detachment and ascent of the un-
expanded male flowers and the continuous upward growth of the female ones.
In both cases means are provided to prevent the access of water to the mature
reproductive organs: in Vallisneria this is effected by means of their travelling to
the surface of the water; in Ottelia by the provision of a special localised at-
mosphere developed by the plant itself.
It remains finally to consider how far it is. possible to explain the occurrence
of such a phenomenon,—how far it is possible to account for the temporary dis-
charge of gas froth the flower during maturation and the cessation of the process
subsequently. A careful consideration of the structural features of the plant
appears to be capable of affording the desired explanation.
It is unnecessary here to enter into full details regarding the structure of
Ottelia, as the plant is one which has been specially dealt with by Chatin in
his "Anatomie Compare des Végétaux." The only important points in regard to
which specimens of the plant, as occurring in Calcutta, differ from the descrip-
tion in the work just mentioned, are that in them there is throughout an entire
absence of the so-called pseudostomata which are described by Chatin as present
in the leaves (Plate VI, Figs. 2, 3), and that the stem, in place of being com-
posed throughout of a continuous dense tissue, is composed of a dense axial
portion, surrounded by a thick peripheral zone, in which the bases of the petioles
and scapes terminate, and which is throughout permeated by a great system of
large, intercommunicating, intercellular spaces. Confining attention to general
points, it is sufficient to state that the plant is throughout characterised by the
enormous development of the system of great unicellular spaces, and by the
entire absence of any special channels for the discharge of gaseous contents
from it. The leaves are composed of delicate, unicellular, epidermal strata, con-
nected with one another by an open network consisting of single rows of cells
(Plate VII, Figs. 1, ,2, 3, 4) surrounding huge intercellular spaces (vide Note E).
The petioles and flower-stalks are of corresponding structure (Plate VIII) and ter-
minate inferiorly in a mass of spongy tissue, forming the peripheral zone of the
short stem, and full of large, intercommunicating, intercellular spaces (Plate VII,
Fig. 5). The sepals and petals agree generally with the ordinary leaves in their
structure. The latter are, however, distinguished naturally by the extreme deli-
cacy of their tissue elements, and by the fact that the cells of both the superior
and inferior epidermis are provided with projecting tubercles, which, in the case
of the inferior epidermis, at all events, more or less assume the characters of
short hairs, and which serve as an important means for securing the adhesion of
extruded bubbles of gas. The entire plant is throughout thus permeated by a
great, continuous, closed system of intercellular cavities, within which excessive
gaseous evolution occurs under the influence of sunlight. The tension of gases
accumulating within the system goes on progressively increasing until it reaches
a point at which discharge is effected at the points of least resistance. Under