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shade, though it is not necessary to believe the Yankee story of the creeper in his country and how a lazy, longlegged man stretching out asleep in the sun awoke to find that a quick-growing creeper had left the wall and was twining round his knees.

The twining plants have points of distinction when compared with creepers carrying tendrils or similar organs. To name one of some importance that twining plants only coil themselves round and climb up upright supports. This distinguishes them from tendrils which can grow horizontally or up and down. The majority of twining plants are no longer able to climb actively if their support forms a smaller angle with the horizon than 45°. A further point of difference lies in the fact that twining shoot-axes wind themselves round the support in a definite direction according to the species of the plant in each case. The hop and honeysuckle take the form of a left-handed screw; the majority of twining plants, however, twine like a right-handed screw-i.e., from the left below to the right above when the plant and its support are looked at from the exterior. The free pendant apex of the growing shoot revolving in nutation behaves much as if groping towards all points of the compass for support and when meeting a support a part of the apex then curves round it and grows spirally up it. The question of torsions in the true axis in a spiral twist makes another serious complication for the observer. In the twining of twining plants some form of geotropism or influence due to gravitation is of the greatest importance; and in a growing twiner on a rod if the whole pot be inverted so that the twining apex is lowermost the youngest coils of the shoot loosen themselves from the rod and the terminal bud becoming free erects itself and again grows upwards close to the rod. A twining plant will make its spiral curves without a support if the terminal but be steadied by a thread and weight over a pulley so that the apex of the shoot is drawn vertically upwards, but a free horizontally sweeping shoot will make no spiral turns at all. It will not be possible to explain the ways of twiners until we can fully understand how gravity and rays of light act upon processes of growth so that they are able to produce geotropic and heliotropic curvatures. The number of twining plants being over 2000 is far greater than those of tendrilplants; there is thus no lack of objects of interest for the many observers still at work upon them.

In connexion with so-called "mechanical necessity" in spiral curves I will call attention to the spiral form of these carpenter's shavings made with an ordinary plane with the iron set square. Sherlock Holmes is dead, killed by his creator, but that ingenious gentleman, if revived, might

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the growth of the nails is encouraged not only by neglect but by moisture. The growth of his nails was probably not greater than that of a first-class Chinese Mandarin who is really cultivated, for the curves of the nails merely became like bird's claws. If only the growth had continued until the nails assumed a spiral form they might have been compared to corkscrews had bottles then been corked in Babylon. A good specimen to illustrate this tendency (in the Museum at Cambridge) is that of the hind hoofs of a sheep which was shot among boggy soil in the Falklands. Each portion of the cloven hoof is of enormous size and length and twisted spirally about two and a half turns, intertwined, moreover, each with the other portion in a complicated twirl. The contortions, however, take the righthanded twist on one side and left-handed on the other. The hoofs of the ox and the horse from the same soil show this tendency to grow and curve. So far as I can observe in the hoofs the direction of the spirals follows the laws of growth as in the koodoo in growing a different spiral curve on the different sides of the body. With so few examples the observation is of only slight value and anyhow does not apply to Nebuchadnezzar's nails-at least, with our present knowledge.

The effect of want of friction and want of resistance in producing a symmetry and unequal length is here suggested by these perversions. Conversely we manage to grow both our legs of the same size and the same length by exposing them to the same resistances during growth. If encouraged the human nail will grow as the usual claw at first and later will begin to take a twist, as in the Chinaman, and the writer well remembers an example in a queer old bachelor who cultivated his little finger nail by covering it with a cot until it became the wondering talk of the town. The cutting of poor Tom Wither's nail caused as much sensation as when in Athens Alcibiades cut off the tail of his dog. Passing in review these objects of interest now before us, the shells, the shavings, the tendrils and twining-plants, the horns of the koodoo and the contorted hoofs of the sheep, some of my remarks upon them may seem trivial and all unsatisfying, but at least of this I am assured, that many of the problems of spiral growth are deep and difficult and touch upon those great laws which regulate the world. Consideration of such problems sets us thinking of the power that "preserves the stars from wrong" and encourages that constant preference for higher thoughts over lower ones which is the true intellectual life.

Cambridge.

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