.Mr Murray on the Physiology of the Fibres of Hoop. 09 
considerable distance along the wall. One of the branches let 
down a long root; and when it had descended jive feel , it subdi- 
vided into smaller ones : at 1 4 inches from this subdivided point, 
they reached a pot, which they seized on, and fastened therein ; 
the branch was now separated from the parent plant, and con- 
tinues in health and vigour. The main root has not changed 
its character, which is the case with some plants, and where the 
roots, thus exposed, become a stem that issues in branches. 
This last curious phenomenon reminds us of the Plane-tree , 
which, from the summit of one of the ruined walls of New Ab- 
bey in Galloway shire (mentioned by Lord Karnes), detached a 
root to the soil below. 
To preserve the healthy functions of the plant, the excretory 
ducts must be preserved soft, and uniformly free ; and this is as 
essential as the supply of the absorbent vessels. The tips of 
the fibres of the hyacinth, for instance, are more opake and 
dense than the other parts, and from hence the fibres elongate ; 
for if such be cut off, the fibres remain stationary at that length. 
Fresh water is necessary. The water-cress (Nasturtium 
officinale ) must be in a constant current, else the plant does not 
thrive ; and when parallel with the stream, it succeeds best. 
Water is essentially necessary, even to the preservation of the 
vitality of the seed, in some cases. In the Trapa natans , 
the fruit inclosing the seeds falls into water, and the seeds must 
be carried immersed therein, where they will root, otherwise the 
vegetative power would be unhinged. 
It is quite unnecessary to quote more examples, illustrative 
of the necessity of a supply of fresh-water, to preserve alive the 
healthy functions of the plants. The quantity may vary in dif- 
ferent plants, but some is always necessary, whether supplied by 
the soil or the atmospheric medium. 
It must not be conceived that I have spoken of any other 
than the mere fibre of the root. The tuber and the bulb, and 
the base of the trunk, may perform a different character. 
The Gloxinia speciosa , and Gesnera bulbosa , grow freely 
from leaves, and form bulbs . 
The Phleum pratense becomes, in a fluctuating soil, the 
Plileum nodosum of some authors, while, in a wet soil, the 
plant is entirely fibrous and luxuriant. 
