40 Mr Murray on the Physiology of the Fibres of Roots. 
Sir James E. Smith found the Alopecurus geniculatus (a root 
naturally fibrous and repent ) possessed of an ovate juicy bulb, 
on the summit of a dry wall. The changes adverted to are es- 
sentially connected with a relationship to water, and have evi- 
dently nothing to do with grosser materials. 
When a bean reposes for some time in distilled water, it 
swells, yet it is still questionable whether water be absorbed ; 
the testa is evidently impervious to water, and the great decrease 
in its specific gravity (a fraction heavier only than distilled 
water) proves, that if any be absorbed, the quantity is very 
small, and the chief purpose it seems to serve, is that of un- 
sealing the orifice, by dissolving the albumen, and softening the 
membranaceous capsule or testa. This allows the carbonic acid, 
developed during the expansion of the plumula, to escape. 
I took two bottles of water from the cisterns which contained 
aquatic plants , in the conservatory at Arley Hall. 
That from the cistern which was most foul and stagnant , was 
submitted to chemical examination. Six fluid ounces, treated 
with lime-water, yielded a precipitate, which proved to be car- 
bonate of lime. When dried, and carefully weighed, it was 
— AO grains; therefore- afforded .22 gr. carbonic acid gas. 
Six fluid ounces submitted to the action of heat, yielded .64,5' 
cubic inches of air, in which a taper burnt dimly , exhibiting a 
slight deterioration ; and when the quantity of decomposed ve- 
getable matter in this cistern is considered, and in which the 
pots , soil , roots , &c. were immersed, it affords a strong argument 
in favour of the important part sustained by aquatic plants. 
This cistern contained Arum collocasia , esculentum , and other 
species. Also the Eryngium aquaticum , &c. 
The cistern where the water seemed most pure and diapha- 
nous, was filled with Nymphcea odor at a ^ ccendea , also Me- 
nyanthes exaltata , and nymphoides , &c. 
Six fluid ounces, mixed with lime-water, gave, in this last, 
» — .25 gr. which = — .11 gr. carbonic acid gas. 
By heat, the same quantity yielded, cubic inch. .30 of a gas ; 
on continued ebullition, a taper plunged into it, burnt in all 
respects as in common air ; consequently it was not materially 
vitiated. 
No doubt, the water in both cisterns must have been deterk 
