NEW AND RARE PLANTS. 
89 
as being the lungs of plants. Grew thought he had discovered in the leaves a number of 
little bags or bladders filled with air. The air was supposed to have entered by inhalation, and 
the bags or bladders were supposed to be analogous in their functions to the cells of the lungs 
of animals. M. Papin introduced into the receiver of an air-pump an entire plant, root, 
stem, and leaf ; but the consequence was that it very soon died. He then introduced a 
plant by the root and stem only, the leaves being still exposed to the influence of the air. 
The plant lived a considerable length of time, and hence he concluded that leaves are 
lungs. But these facts are far from being sufficient to settle the point in question, and we 
introduce them, not so much with a view to show their inadequacy, as to show that the 
doctrine, even if founded in truth, could not have been satisfactorily demonstrated by any 
experiments that were practicable at that time. 
" It is to the modern improvements in pneumatic chemistry (and to them alone) that we 
are indebted for our knowledge of the real functions of the leaves of plants, and of their 
analogical resemblance to the lungs of animals, it being now proved indisputably that the 
leaves of plants not only contain air, but do both inhale and respire it. It was the opinion 
of Priestley that they inhale it chiefly by their upper surface ; and it has been shown by 
Saussure that their inhaling power depends entirely upon the integrity of their organisation. 
A bough of Cactus opimtia detached from the plant and placed in an atmosphere of common 
air, inhaled in the course of a night four cubic inches of oxygen ; but when placed in a 
similar atmosphere, after being cut to pieces and pounded in a mortar, no inhalation took place. 
" Yet it may be said that the doctrine of vegetable respiration is still involved in some- 
thing of mystery, as the existence of pores is doubted by botanists of high reputation, even 
in what is called stomafa ; and as the occurrence of stomata is but a very rare phenomenon 
in the epidermis of roots, flowers, or fleshy fruits, or bulbs, which, after all, will not thrive or 
ripen well, if wholly deprived of air. But the recent experiments of M. Dutrochet have 
shown that the intervention of visible pores is not at all necessary, whether to the imbibi- 
tion of moisture, or to the inhalation of gases, or whether in the case of animal or vegetable 
membrane. The liquid, or the gas, seems thus to enter by the means of the agency 
of organic molecular infiltration, a power prodigious in its capabilities, but not easily 
accounted for. Dutrochet attributes it to what he calls endosmose, that is, a rush inwards of 
a less dense to a more dense fluid excited by electricity. His experiments and hypothesis 
will be specified and examined under the article of the Ascent of the Sap, or its Cause. 
In the mean time we will content ourselves by merely saying that we do by no means re- 
gard his conclusions as following legitimately from his premises ; nor can we regard any 
cause accounting for the effect in question as being at all adequate to its object, which does 
not involve the agency of a power of a higher order than that either of capillary attraction 
or of electricity ; namely, that of the agency of the living energies of the plant.'' 
NEW AND RARE PLANTS, 
FIGURED IN THE LEADING BOTANICAL PERIODICALS FOR APRIL. 
CLASS I.— PLANTS WITH TWO COTYLEDONS (DICOTYLEDONEiE). 
THE BEAN TRIBE {Legitminosce). 
MucuNA PRURiENS. West Indian Cow-itcli Plant. The principal part of 
the stinging substance which is sold in shops under the name of " cow-itch," is 
probably obtained from this plant, which grows naturally and abundantly in many 
VOL. V. NO. Lll. N 
