Page:Popular Science Monthly Volume 66.djvu/226

222 The Climax plum is a cross of the bitter, flat, tomato-shaped Chinese plum, Prunus simoni, and the Japanese plum, Prunus triflora. The Chinese plum produces almost no pollen; hardly a grain of it is known, not more than one could put in his eye without feeling it; but the whole fruit shipping industry of the world has been changed by this hybrid plum (Climax) produced by it. With many crosses of many things it is certain that forms of great importance will come out every year, though never in profusion.

In developing a spineless cactus for stock-feeding, selections were made from the three hardy northern species, Opuntia rafinesquii, O, mesacantha and O. vulgaris; these were crossed with O. tuna, O. ficusindica and with a Small opuntia from Central America, almost thornless.

The cactus has smooth cotyledons, but the first bud is covered with thorns. These thorns have also been eliminated by selecting the smoothest individual seedlings without crossing. Crossing in this case generally interrupts the process, as it brings out well-fixed ancestral traits, but later, to combine the best qualities of several species, crossing and selection must be resorted to. Examples seen were shoots of the original stock, prickly; the second generation, slightly prickly; the third, without thorns; and later the spicules even within the substance of the cactus have been removed so as to make the cactus very excellent food for cattle. This will have very great value in the arid regions. Some cacti lose the thorns on the plant but retain them on the fruit; others vice versa. By crossing and extensive and intensive selection a cactus may be improved in various ways besides being deprived of thorns and of the internal spicules in six or less generations; these, by means of cuttings, may be multiplied rapidly to any extent, but the process, to be complete, generally takes longer. This thornless cactus should prove of very great value in the development of desert regions as Arizona or Sonora, as the quantity of food produced per acre is enormous.

The Bartlett plum has the flavor of a Bartlett pear, but even more strongly developed. The 'rice seed' plum has extremely small seeds. The stoneless plum is a cross of the French prune with a wild plum having the stone almost eliminated by a fortuitous variation. The result thus far is a great number of stoneless plums of good size, but in flavor inferior to the best cultivated ones. These are being crossed again to improve the flavor, and new selections made.

Crossing the Japan and the New England chestnut (Castanea