OF PLANTS. 289
from the Edinburgh New Philosophical Journal, April-July, 1835), in which he shows with certainty, by means of new and very careful experiments, that roots of plants have, at any rate to a certain degree, the power to make choice from those substances in the soil which present themselves to their surface. 1
1 In this connection I may mention an analysis of an entirely different kind, given by the French Academician Babinet in an article in which he treats of the seasons on the planets. It is contained in the Number, of the 15th January, 1856, of the Revue des Deux Mondes, and I will give the chief substance of it here in translation. The object of it is to refer to its direct cause the well-known fact, that cereals only thrive in temperate climates. "If grain did not necessarily perish in winter, if it were perennial, it would not bear ears, and there would be no harvest. In the hotter portions of Africa, Asia and America, where no winter kills the grain, these plants grow like grass with us: they multiply by means of shoots, remain always green, and neither form ears nor run to seed. In cold climates, on the contrary, the organism of these plants seems by some inconceivable miracle to feel, as it were by anticipation, the necessity of passing through the seed-phase in order to escape dying off in the winter season (L' organisme de la plante, par un inconcevable miracle, semble pressentir la nécessité de passer par l'état de graine, pour ne pas périr complètement pendant la saison rigoureuse). In a similar way, districts which have a "droughty season," that is to say a season in which all plants are parched up with drought, tropical countries, for instance Jamaica, produce grain because there the plant, moved by the same organic presentiment (par le même pressentiment organique), in order to multiply, hastens to bear seed at the approach of the season in which it would have to dry up." In the fact which this author describes as an inconceivable miracle, we recognise a manifestation of the plant's will in increased potency, since here it appears as the will of the species, and makes preparations for the future in a similar way to animal instinct, without being guided by knowledge of that future in doing so. Here we see plants in warmer climates dispensing with a complicated process to which a cold climate alone had obliged them. In similar instances animals do precisely the same thing, especially bees. Leroy in his admirable work Lettres Philosophiques sur l'Intelligence des Animaux " (3rd letter, p. 231) relates, that some bees which had been taken to South America continued at first to gather honey as usual and to build their cells just as when they were at home; but that when they gradually became aware that plants blossom there all the year round, they left off working. The animal world supplies a fact analogous to the above mentioned change in the mode of multiplying in cereals. This is the abnormal mode of propagation for which the aphides [plant lice] have long been noted. The female aphide, as is well known, propagates for 10-12 generations without any pairing with the male, and by a variety of the ovoviviparous process. This goes on all summer; but in autumn the males appear, impregnation takes place, and eggs are laid as winter quarters for the whole species, since it is only in this shape that it is able to outlive the winter. [Add. to 3rd ed.]
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