NANISM OR DWARFING

New Zealand Mail, 5 February 1902, Page 62

NANISM OR DWARFING

Nanism, or dwarfing, as well as gigantism, writes Geo. Henslow, in the “Gulden/’ are affections of plants, just as they are of human beings, and it is difficult to account for them in the one case as in the other. Of course, one puts aside the temporary or artificial dwarf-

ing due to starvation, as well as the remarkable stunted forms of trees .grown by the Japanese. But while dwarfs and giants appear among seedlings of plants which are normally of a particular size, it is difficult to see why they occur at all. We know from experience that they may be hereditary, as in dwarf French beans and peas, as well as “Cupids” among sweet peas, etc. Nanism is more frequent under cultivation than among wild plants, though it has become a permanent feature in certain trees of Arctic and Antarctic regions, as in beeches and pines. Linnaeus, indeed, thought that arid conditions were necessary. They' certainly are in some cases, but it is not so, of course, with the appearance of dwarfs in a well cultivated moist garden. Nanism is more frequent in annuals than in perennials. Perhaps this is so only because more annual plants are raised and in more varied conditions than perennials. The natural tendency to fix itself varies greatly. Some dwarfs remain true from the second year, others require from two to six years of selection and isolation before the strain can become established ; but the general rule seems to be that the longer the species lias been in cultivation the shorter the time does it take to fix a new variety and so establish a race.

To produce dwarfs, M. Verlot suggested the following process as worth trial:—First sow the best of these dwarfs, and the process repeated year j after year; there will ultimately be de- j veloped a tendency to nanism. As I another practical method, the flowers of i the plant it is wished to make dwarf j should be pollinated by the stamens of ! the dwarfest of its kind, and the pro- J bability is that at least some of the 01F- j spring will show the desired tendency. Mr M’Nab found that “the best dwarf | varieties of rhododendron are those obtained by using pollen taken from Ihe smaller stamens. This result is very suggestive, because the orders Leguminosae, Labiatae, Scrophularineae and allies, as well as Belargonia, etc., will j supply ample material for experimenta- | tion, which would test the generality of the inference from Mr M’Nab’s experience.