Page:Popular Science Monthly Volume 27.djvu/497

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ON LEAVES.

cal germinal spot was again prepared for in advance, by showing the child the cicatricule of a hen's egg, lying like the Mediterranean basin, on a globe. Thirdly, study of the systematized topography of the globe constituted the best initiation into the study of all topographical relations, including those involved in animal anatomy, and therefore this consideration was not among the least important. Fourthly, an important elementary philosophical training was obtained, as the child learned to analyze into their details the largest pictures offered by the globe, and to arrange these details into orders of successive degrees of generalization. Great care was taken that all pictures or outlines of the same magnitude, and hence visible at the same distance, should be studied at the same time, and not associated with less conspicuous details that required more minute attention. This rule of following successive degrees of generalization in geographical analysis is most imperfectly observed in text-books. It imposes itself in study of the relief-globe.

[To be continued.]

 

ON LEAVES.
By Sir JOHN LUBBOCK.
II.

WE have hitherto been considering, for the most part, deciduous trees. It is generally supposed that in autumn the leaves drop off because they die. My impression is that most persons would be very much surprised to hear that this is not altogether the case. In fact, however, the separation is a vital process, and, if a bough is killed, the leaves are not thrown off, but remain attached to it. Indeed, the dead leaves not only remain in situ, but they are still firmly attached. Being dead and withered, they give the impression that the least shock would detach them; on the contrary, however, they will often bear a weight of as much as two pounds without coming off.

In evergreen species the conditions are in many respects different. When we have an early fall of snow in autumn, the trees which still retain their leaves are often very much broken down. Hence, perhaps, the comparative paucity of evergreens in temperate regions, and the tendency of evergreens to have smooth and glossy leaves, such as those of the holly, box, and evergreen-oak. Hairy leaves especially retain the snow, on which more and more accumulates.

Again, evergreen leaves sometimes remain on the tree for several years; for instance, in the Scotch pine three or four years, the spruce and silver-fir six or even seven, the yew eight, A. pinsapo sixteen or seventeen, araucaria and others even longer. It is true that during