TRUE DARWINISM 169 



if brought above the surface ; similarly a leaf ordinarily fitted 

 for living in air, soon perishes if kept under water ; but if 

 either plant be allowed to develop its leaves from the leaf-bud 

 stage in the medium, opposite in kind to its usual one, it may 

 grow and adapt itself during its development to that medium till 

 it is fully developed, as often occurs with the water-crowfoot. 



In order to ascertain, therefore, whether the peculiarities 

 of any plant are really due to the environment, as the efficient 

 cause to incite the variability of the plants, many experiments 

 have been made, and in each case the results invariably showed 

 that when a plant is grown out of its usual surroundings and 

 in another of a very different kind ; it either fails to grow, or, 

 if it succeed, it does so by putting on just those structures 

 characteristic of the plants normally growing in the environment 

 in question. 



Thus, with regard to each of the groups above mentioned, 

 it is found, e.g., that if spiny plants of a dry soil or climate be 

 grown in a moist atmosphere and soil, the development of 

 spines is at once checked; the plants become less and less 

 spinescent until the spiny processes cease to be formed al- 

 together. If very hairy plants, characteristic of a dry locality, 

 be grown in water or in a constantly moist situation, they lose 

 their hair to a greater or less degree and so resemble water 

 plants which are normally hairless. If a plant usually developing 

 a tall flowering stem in lowlands be planted on high altitudes, 

 as of the Alps, it cannot develop it ; but becomes a dwarf, like 

 ordinary Alpine plants, the anatomy changing correspondingly. 

 If garden or wild plants like cress be watered with a solution 

 of salt, the leaves develop themselves thick and fleshy like 

 those of an ordinary maritime plant subject to the salt spray 

 of the sea. Conversely the samphire has borne flat and thin 

 leaves when cultivated in a garden far from the sea-side. 

 These are but a very few samples of an abundance of illustra- 

 tions furnished by experiments, which fully justify the belief 

 that the normal characteristics of plants are in every case due 

 to the environment, as Dr. Weismann maintains ; but contrary 



