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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 Kolpakoicskyana* 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. 



Illusteations 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, steins, and leaves to either 

 medium, air or water. If they be transferred from one to the 



* Card. Chron., 1896, p. 586. Figs. 93, 94. 



