396 M.S.B. Schnetzler on the Aériferous 
In the lake of Escoubous, situated upon the summit of the 
Hautes-Pyrénées, at 2052 metres above the level of the ocean, 
there lives a very remarkable variety of Ranunculus aquatilis. 
It forms a sort of very extended turf, moored to the bottom of 
the water by the radicles which shoot out even at the extremity 
of its stems—side by side with broad carpets of a blackish-green 
colour, formed by Tremelloid Ulv. Here, in opposition to the 
laws which caus¢ aquatic plants to seek the open air in order to 
flower and accomplish the act of reproduction, it remains con- 
stantly immersed, far from the margins, where the severity of 
the frosts might destroy it, and far from the great depths, where 
it would no longer find the light necessary for its vegetation*; 
here it expands its finely divided leaves and its white corollas 
with their golden bottoms, and here it is fecundated and repro- 
duces itself without ever attempting to reach the surface. The 
possibility of fecundation is shown by a bubble of air produced 
during the work of vegetation and retained between the petals 
before their full expansion, in which the anthers project their 
pollen (Guérin, Dict. d’Hist. Nat. tome viii. p. 465). 
The evolution of gas in closed cavities, which we observe in a 
certain number of aquatic plants before the expansion of the 
flower, is evidently in relation to what it has been agreed to call 
vegetable respiration. During this operation the plant not only 
takes carbonic acid from the air .or water, but it also absorbs, 
through all its parts, oxygen, which combines with the carbon 
of certain vegetable matters to form carbonic acid. The chemical 
action of the solar light induces the decomposition of the car- 
bonic acid absorbed, as well as of that formed in the plant. The 
carbon is fixed in the plant by combining with the elements of 
water, nitrogenous matters, &. The oxygen is evolved. The 
stomata appear to play an important part in respiration; never- 
theless, according to the investigations of Duchartre, there is no 
definite relation between the number and size of the stomata 
and the quantities of gas evolved by plants when exposed to the 
sun. In certain trees which have a dry and leathery texture 
there is an inverse ratio between the considerable number of the 
stomata and the weakness of the evolution of gas.. Moreover 
what proves that the gases exhaled by plants are not evolved 
solely through the stomata is, that we see them issue from the 
cells of the epidermis of the upper surface of leaves in plants in 
which this surface has no stomata, when the leaves are immersed 
in water. We have already demonstrated a similar evolution 
from the immersed leaves of Utricularia. In entirely submerged 
aquatic plants the leaves are destitute of stomata, and absorption 
* The plant in question does not occur either at the margin or at great 
depths, because it cannot exist in either of these positions. 
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