REMARKS ON SOME VEGETABLE PHENOMENA. 
301 
or organ composing the vegetable fabric has rudimental identity before 
it is developed; and, therefore, that growth is nothing more than 
simple distension. The notion is, however, completely opposed to the 
opinion of those who imagine that every part of the structure of plants 
is formed of what is called elaborated sap. 
Whether the idea as above stated be reasonable or not, or whether the 
opposition to the opinion of others be or be not justifiable, is not the 
direct object of these remarks ; they point to another question, which 
may, perhaps, be worth the physiologist’s consideration. 
In witnessing the development or growth of the new layers of wood 
and bark every year added between the layers of these members formed 
in the preceeding year, wa invariably observe that it, the swelling mem¬ 
brane or new growth, increases faster downwards than it is extended 
in any other direction. For instance, let us suppose a piece of bark two 
inches square to be removed from the stem of a tree of any kind or size 
in the month of March, when it will part easily from the wood. The 
edges of the wound is composed of as many layers of liber as the tree is 
years old, and underneath all these lies the membrane which will be 
distended into new layers of liber and wood in the ensuing summer. The 
membrane at this time is hardly perceptible, appearing like thin mucus 
or jelly; but if occasionally examined, it will be observed to harden in 
the air, and remain motionless till about the end of May, sooner or later, 
according to the forwardness of the season. About that time, however, 
it may be seen protruding from under the bark all round the wound, 
and will continue so to do till the growth ceases in the autumn. 
When this happens, it will be seen that the new member has proceeded 
much further dotvnward from the upper lip of the wound, than it has 
at the sides, or at the bottom ; and this the new layers of every succeed¬ 
ing year will continue to do, till the wound is wholly covered and 
healed over. 
Many other instances may be given of the tendency of the new 
member to descend with more rapidity than it is extended in any other 
direction. The manner in which layers and cuttings are usually seen 
to make roots, is a familiar example : first, there appears the membrane 
alluded to descending and forming what is called a callosity at the base 
of the cutting, whence fibres are afterwards emitted. The same kind of 
swelling takes place round, and particularly at the point of the tongue 
of a layer, before it ejects radicles ; though it may happen that cuttings 
as wells as layers will be furnished with roots without any callosity 
being first formed. 
These are unquestionable proofs that the vital membrane of a plant 
descends with more facility than it, as already observed, is enlarged in 
any other direction. It is a long established fact, known to every prac- 
