The theory of this curious vegetable fact has been esteemed difficult, but receives great light from the foregoing account of the individuality of buds. A flower-bud dies, when it has perfected its seed, like an annual plant, and hence requires no place on the bark for new roots to pass downwards; but on the contrary leaf-buds, as they advance into shoots, form new buds in the axilla of every leaf, which new buds require new roots to pass down the bark, and thus thicken as well as elongate the branch, now if a wire or string be tied round the bark, many of these new roots cannot descend, and thence more of the buds will be converted into flower-buds.
It is customary to debark oak-trees in the spring, which are intended to be felled in the ensuing autumn; because the bark comes off easier at this season, and the sap-wood, or alburnum, is believed to become harder and more durable, if the tree remains till the end of summer. The trees thus stripped of their bark put forth shoots as usual with acorns on the 6th 7th and 8th joint, like vines; but in the branches I examined, the joints of the debarked trees were much shorter than those of other oak- trees; the acorns were more numerous; and no new buds were produced above the joints which bore acorns. From hence it appears that the branches of debarked oak-trees produce fewer leaf-buds, and more flower- buds, which last circumstance I suppose must depend on their being sooner or later debarked in the vernal months. And, secondly, that the new buds of debarked oak-trees continue to obtain moisture from the alburnum after the season of the ascent of sap in other vegetables ceases; which in this unnatural state of the debarked tree may act as capillary tubes, like the alburnum of the small debarked cylinder of a pear-tree abovementioned; or may continue to act as placental vessels, as happens to the animal embryon in cases of superfetation; when the fetus continues a month or two in the womb beyond its usual time, of which some instances have been recorded, the placenta continues to supply perhaps the double office both of nutrition and of respiration.]
[And bend to earth. l. 466. Mr. Hitt in his treatise on fruit trees observes that if a vigorous branch of a wall tree be bent to the horizon, or beneath it, it looses its vigour and becomes a bearing branch. The theory of this I suppose to depend on the difficulty with which the leaf-shoots can protrude the roots necessary for their new progeny of buds upwards along the bended branch to the earth contrary to their natural habits or powers, whence more flower-shoots are produced which do not require new roots to pass along the bark of the bended branch, but which let their offspring, the seeds, fall upon the earth and seek roots for themselves.]
[With new prolific power. l. 467. About Midsummer the new buds are formed, but it is believed by some of the Linnean school, that these buds may in their early state be either converted into flower-buds or leaf-buds according to the vigour of the vegetating branch. Thus if the upper part of a branch be cut away, the buds near the extremity of the remaining stem, having a greater proportional supply of nutriment, or possessing a greater facility of shooting their roots, or absorbent vessels, down the bark, will become leaf-buds, which might otherwise have been flower-buds. And the contrary as explained in note on l. 463. of this Canto.]
[Closed in the style. l. 469. "I conceive the medulla of a plant to consist of a bundle of nervous fibres, and that the propelling vital power separates their uppermost extremities. These, diverging, penetrate the bark, which is now gelatinous, and become multiplied in the new gem, or leaf-bud. The ascending vessels of the bark being thus divided by the nervous fibres, which perforate it, and the ascent of its fluids being thus impeded, the bark is extended into a leaf. But the flower is produced, when the protrusion of the medulla is greater than the retention of the including cortical part; whence the substance of the bark is expanded in the calyx; that of the rind, (or interior bark,) in the corol; that of the wood in the stamens, that of the medulla in the pistil. Vegetation thus terminates in the production of new life, the ultimate medullary and cortical fibres being collected in the seeds." Linnei Systema Veget. p. 6. edit. 14.]
2. "Where cruder juices swell the leafy vein,
Stint the young germ, the tender blossom stain;
On each lop'd shoot a softer scion bind,
480 Pith press'd to pith, and rind applied to rind,
So shall the trunk with loftier crest ascend,
And wide in air its happier arms extend;
Nurse the new buds, admire the leaves unknown,
And blushing bend with fruitage not its own.
[Nurse the new buds. l. 483. Mr. Fairchild budded a passion-tree, whose leaves were spotted with yellow, into one which bears long fruit. The buds did not take, nevertheless in a fortnight yellow spots began to shew themselves about three feet above the inoculation, and in a short time afterwards yellow spots appeared on a shoot which came out of the ground from another part of the plant. Bradley, Vol. II. p. 129. These facts are the more curious since from experiments of ingrafting red currants on black (Ib. Vol. II.) the fruit does not acquire any change of flavour, and by many other experiments neither colour nor any other change is produced in the fruit ingrafted on other stocks.
There is an apple described in Bradley's work which is said to have one side of it a sweet fruit which boils soft, and the other side a sour fruit which boils hard, which Mr. Bradley so long ago as the year 1721 ingeniously ascribes to the farina of one of these apples impregnating the other, which would seem the more probable if we consider that each division of an apple is a separate womb, and may therefore have a separate impregnation like puppies of different kinds in one litter. The same is said to have occurred in oranges and lemons, and grapes of different colours.]
485 "Thus when in holy triumph Aaron trod,
And offer'd on the shrine his mystic rod;
First a new bark its silken tissue weaves,
New buds emerging widen into leaves;
Fair fruits protrude, enascent flowers expand,
490 And blush and tremble round the living wand.
XIII. 1. "SYLPHS! on each Oak-bud wound the wormy galls,
With pigmy spears, or crush the venom'd balls;
Fright the green Locust from his foamy bed,
Unweave the Caterpillar's gluey thread;
495 Chase the fierce Earwig, scare the bloated Toad,
Arrest the snail upon his slimy road;
Arm with sharp thorns the Sweet-brier's tender wood,
And dash the Cynips from her damask bud;
Steep in ambrosial dews the Woodbine's bells,
500 And drive the Night-moth from her honey'd cells.
So where the Humming-bird in Chili's bowers
On murmuring pinions robs the pendent flowers;
Seeks, where fine pores their dulcet balm distill,
And sucks the treasure with proboscis-bill;
505 Fair CYPREPEDIA with successful guile
Knits her smooth brow, extinguishes her smile;
A Spiders bloated paunch and jointed arms
Hide her fine form, and mask her blushing charms;
In ambush sly the mimic warrior lies,
510 And on quick wing the panting plunderer flies.