P.T.W.
CHANGES DURING THE MATURATION OF FRUIT.
The sap is changed into a viscid fluid, which circulates under the bark: this is called cambium. When it is too abundant it is effused, part of its water evaporates, and it becomes gum. If the vital circle is not interrupted, the fluid traverses the branches, and the peduncle arrives in the ovary, and constitutes the pericarp. In this passage it is partly modified: it appropriates to itself the oxygen of its water of composition; hence the malic, citric, and tartaric acids. As the fruit becomes developed, the pellicle thins, becomes transparent, and allows both light and heat to exercise a more marked influence. It is during this period that maturation commences. The acids react on the cambium, which flows into the fruit, and, aided by the increased temperature, convert it into saccharine matter; at the same time they disappear, being saturated with gelatine, when maturation is complete.—London Medical and Surgical Journal.
We may here observe that in a recent paper, by Mr. J. Williams, in the Transactions of the Horticultural Society, the cause of apples becoming russet is attributed to the alternating temperature, light, shade, dryness, and moisture, which occur many times in the course of a day, when July or August is showery. Continued rain, preceded and followed by a cloudy sky, does not seem to produce the same effect, but the sudden, intense light which commonly succeeds a shower at the time the fruit is wet, injures the skin, and occasions small cracks, like the network upon a melon.
MIGRATION OF BIRDS.
Whatever theory of instinct may be finally fixed upon as the most correct and philosophical, (to account for the migratory movements of birds,) it is obvious that we cut rather than untie the gordian knot when we talk of the foresight of the brute creation. We might as well talk of the foresight of a barometer. There can be little doubt that birds, prior to their migratory movements, are influenced by atmospherical changes, or other physical causes, which, however beyond the sphere of our perceptions, are sufficient for their guidance. That they are not possessed of the power of divination may be exemplified by the following instance. The winter of 1822 was so remarkably mild throughout Europe, that primroses came generally into flower by the end of December,—rye was in ear by the middle of March, and vines, in sheltered situations, blossomed about the end of that month,—so that an assured and unchecked spring was established at least four or five weeks earlier than usual;—yet neither the cuckoo nor the swallow arrived a single day before their accustomed periods. They are indeed, beautifully and wisely directed,—"Yea, the stork in the heavens knoweth her appointed times; and the turtle, and the crane, and the swallow, observe the time of their coming."—(From a delightful paper upon American Ornithology, in the Quarterly Review, just published.)