$8 Mr Murray on the Physiology of the Fibres of Roots. 
most universally received one, namely, that the fibres of the 
root are absorbents, and the canals which convey the proper 
food of plants to the vegetable system. 
Besides the Epidendron which grows on the stem of the 
Sterculia Balangkas , we find the Dendrobium Picrardii , which 
succeeds very well if fastened to a tree, and artificially ir- 
rigated. Some species of Orchis grow luxuriantly on the 
barren rock. I have preserved leaves of the Bryophyllum ca- 
lycinum , fretted with young plants around its indented fringe, 
for fourteen months in my pocket-book. 
The lateral branches of a tree on one side, which over-arched 
a rich compost, were, compared with those on the other side, re- 
markably luxuriant ; and if the branches be carried over a wall , 
and the soils on either side differ in quality, the tree will exhi- 
bit a corresponding variety. Moreover, the same luxuriance and 
permanence are exhibited in meadow herbage, whether the ma- 
nure be scattered over the superficies, or applied immediately 
to the roots. 
Kir wan, in his Geological Essays, has adverted to experiments, 
which prove, that the fertility of a soil has reference to its rela- 
tions to moisture, rather than any thing else. 
In Captain Tuckey’s “ Narrative,” London, 4to, 1818, p. 18. 
is the following remark, made at Porto Pray a : 66 A very large 
tamarind tree, growing out of the crevice of a naked rock, and 
the profusion of fruit on the cocoa-nut, banana and papaw trees, 
where there is not a foot of soil, prove, that in this climate 
water is the grand principle of vegetation.” 
I saw a very interesting phenomenon connected with the pre- 
ceding facts, at Arley Hall, the seat of the Earl of Mountnorris. 
A Cactus triangularis had grafted on it, two of the C. 
pliyllanthoides , about a foot distant from each other; also 
one of the C. flabdliformis , about 7 feet high on the stem ; 
and one of C. grand form, say 4 feet distant from the lat- 
ter. The C. flabdliformis has been inserted three years, 
and has flowered much finer than when growing on its proper 
roots. The others have’ been attached not more than a year 
and a-half, and have not yet flowered. No fibres appear at the 
point of insertion. 
Another plant of Cactus triangularis had extended itself to a 
