the true Sap of Trees is deposited during Winter. 97
Ingekhouz prove that their action on the air which surrounds them is very essentially different from that of full grown leaves. It is true that buds in many instances will vegetate, and produce trees, when a very small portion only of albur- num remains attached to them ; but the first efforts of vege- tation in such buds are much more feeble than in others to which a larger quantity of alburnum is attached, and therefore we have, in this case, no grounds to suppose that the leaves derive their first nutriment from the crude sap.
It is also generally admitted, from the experiments of Bonnet and Du Hamel, which I have repeated with the same result, that in the cotyledons of the seed is deposited a quantity of nutriment for the bud, which every seed contains ; and though no vessels can be traced* which lead immediately from the cotyledons to the bud or plumula, it is not difficult to point .out a more circuitous passage, which is perfectly similar to that through which I conceive the sap to be carried from the leaves to the buds, in the subsequent growth of the tree ; and I am in possession of many facts to prove that seedling trees, in the first stage of their existence, depend entirely on the nutriment afforded by the cotyledons; and that they are greatly injured, and in many instances killed, by being put to vegetate in rich mould.
We have much more decisive evidence that bulbous and tuberous rooted plants contain the matter within themselves which subsequently composes their leaves ; for we see them vegetate even in dry rooms, on the approach of spring ; and many bulbous rooted plants produce their leaves and flowers with nearly the same vigour by the application of water only,
♦ Hedwig. MDCCCV. O
