Physical Structure of Plants. 61 
coincides precisely with the result. There cannot be a more 
complete proof of the absence of any specific antagonism or 
vital force than is presented in these and similar experiments; 
the gases expired are distinctly the same as should flow out by © 
exOsmosis. 
34. The property of evolving nitrogen in the families of fun- 
goid Cryptogamia, associates them to the Vasculares, and shows 
that whatever points of difference may exist between these divis- 
ions of the vegetable kingdom in other respects, there is in this 
respect an uniformity of action of the greatest interest, as the 
chemical changes leading to the separation of nitrogen, belong to 
all living plants. The large absorption of oxygen in fungi is a 
prominent function, they do not appropriate it in the same limited 
way as other plants, but are even capable of decomposing water for 
its attainment, the hydrogen being liberated. This phenomenon 
has been witnessed by Humboldt, De Candolle, and M. Marcet. 
35. In the researches of Th. de Saussure on germination, an 
interesting case of physical penetration occurs, which has pro- 
duced some confusion among theorists. In the Memoires de la 
Societé Physique, &c., de Genéve, t. vi, p. 545, it is stated that 
seeds germinating in common air absorb nitrogen gas; but that 
when the process is conducted in an atmosphere of equal volumes 
of nitrogen and oxygen, none is absorbed. This is precisely the 
result to be expected, on the hypothesis that the absorption of 
gases is a physical phenomenon: so long as the atmosphere with- 
out contains 80 per cent. nitrogen, this gas is absorbed to produce 
acompensation in the plant gas, but when it is reduced to 50 per 
cent. absorption ceases, the seeds and growing parts, containing a 
Sufficiency in their pores. : 
6. How far confusion may arise in questions of vegetable 
physiology, if we overlook the physical laws of penetration, is 
made evident by the contradictory statements of Saussure, Ingen- 
housz, Plenk and De Gandolle, on the absorption and evolution of 
' ases by the green parts of plants placed in artificial atmospheres. 
Les parties verts laissent moins de gas oxigéne dans le gas hydro- 
Sene que dans le gas azote; elles ne paraissent, contre |’assertion 
d'Ingenhousz, absorber ni l’un ni l’autre. I] parait aussi certain, 
malgré l’assertion d’Plenk, qu’elles n’exhalent point de gas azote, 
sant dans quelques cas, par les corolles—De Candolle Physiolo- 
Be Veg., t. i, p. 133. 
