winding and they will twine round each other. Duhamel placed some Italian beans in a cylinder filled with moist earth; after a little while they began to germinate and naturally sent their _plumula_ upwards in the direction of the light and their _radicula_ downwards into the mould. After a few days the cylinder was turned round to the extent of a quarter of its circumference and the same process was repeated until it had been turned completely round. The beans were then removed from the earth, when it was found that both _plumula_ and _radicula_ had twisted at each turn that had been given, in order to adapt themselves to it, the one endeavouring to rise perpendicularly, the other to descend, so that they had formed a complete spiral. Yet, notwithstanding this natural tendency to descend, when the soil below is too dry, roots will grow upwards in order to reach any moist substance which may be lying higher than themselves." [252] These have been translated for the "Bibliothèque Britannique, Section des Sciences et Arts," vol. lii. [253] Treviranus, "Die Erscheinungen und Gesetze des Organischen Lebens" (Phenomena and Laws of Organic Life), vol. i. p. 173. [254] Brandis, "On Life and Polarity," 1836, p. 88, says: "The roots of rock-plants seek nourishing mould in the most delicate crevices of rocks. These roots cling to a nourishing bone in dense clusters. I saw a root whose growth was intercepted by the sole of an old shoe: it divided itself into as many fibres as the shoe-sole had holes--those by which it had been stitched together--but as soon as these fibres had overcome the obstruction and grown through the holes, they united again to a common stem." And p. 87: "If Sprengel's observations are confirmed, even mediate relations are perceived (by plants) in order to obtain this end (fructification): that is to say, the anthers of the _nigella_ bend down in order to put the pollen on the bees' backs, and the pistils bend in like manner to receive it from the bees." [Add. to 3rd ed.] In Froriep's "Memoranda" for 1833 (No. 832) there is a short article upon the locomotivity of plants: in poor soil, where good mould lies near at hand, many plants will send out a shoot into the good mould; after a time the original plant then withers, but the offshoot prospers and itself becomes the plant. By means of this process, a plant has been known to climb down from a wall. In the same periodical (1835, No. 981) is to be found a communication from Professor Daubeny, of Oxford (taken 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.[255]