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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
when grown at high altitudes and latitudes. Plants of arid 
districts gradually lose their spiny and poverty-stricken appear¬ 
ances when grown in a rich and moist soil. 
Hence it is obviously more likely that one would induce 
plants to vary by transferring them to as different external 
conditions as possible. Mr. Elwes informed me that the many 
bulbous plants he brought from the East change so in all their 
parts in his garden, that they can scarcely be recognised after 
three or four years; as, e.g., Tulipa Kolpakoivskyana.* Of 
course, great differences exist in the natural capacity of plants 
to change ; some are very refractory, others supply numerous 
cultivated varieties ; but every experience tends to show that all 
plants can vary if a sufficiently active environment be provided 
to call out their latent powers of response. 
Illustrations of Rapid Changes in Structure.— 
From Dry to Moist Conditions. —One of the most marked and 
comparatively sudden alterations of structure that take place on 
a change of environment is seen in that of inhabitants of dry, 
poor soils with a dry atmosphere, when they are removed to a 
moist one. Thus a common feature of not a few plants of the 
former condition is to be spinescent; whether the spines be 
branches, as in the Rest-harrow, or leaves, as in the Barberry. 
Experiments have shown that if the Rest-harrow ( Ononis spinosa) 
be grown, either from seed or from cuttings, in a moist soil and 
atmosphere, the spines soon cease to be formed, and the plants 
assume more or less the character of the wild and spineless 
form, 0. inermis or 0. repens. Similarly the leaf-spines of 
the Barberry will develop out into true leaves under similar 
conditions; while hairiness, a characteristic of drought, dis¬ 
appears. 
Analogous results have occurred when wild plants bearing 
spines have been cultivated in, of course, a good soil: when 
they become non-spinescent, as Pears and Plums and some 
Roses. 
From an Aquatic to a Land Soil. —Many plants are 
amphibious, i.e., though usually aquatic and wholly or partly 
submerged, they can grow on land equally well by adapting the 
minute structures of their roots, stems, and leaves to either 
medium, air or water. If they be transferred from one to the 
* Card. Chron., 1896, p. 586. Figs. 93, 94. 
