Boor I.' DISTRIBUTION OF VEGETABLES. 269 



1725. The Epidendron flos acHs Is regarded also by botanists as a parasitical plant, because it is generally 

 found growing on other trees. But as it is found to grow in old tan, it probably derives only support 

 from the bark of trees, and not nourishment. 



1726. Light is a body which has very considerable influence on the structure of vege- 

 tables, and some also on their habitation. The fungi do not require tlie usual interludes 

 of day, in order to decompose carbonic acid gas, and can live and thrive with little or no 

 light. In green plants, which require the action of light, the intensity required is very 

 different in diflferent species ; some require shady places, and hence the vegetable inha- 

 bitants of caves, and the plants which grow in the shades of forests ; others, and tlie 



freater number, require the direct action of the sun, and grow in exposed elevated sites. 

 )e CandoUe considers that the great difficulty of cultivating Alpine plants in the gardens 

 of plains, arises from the impossibility of giving them at once the fresh temperature and 

 intense light which they find on high mountains. 



Sect. III. Civil Causes affecting the Distribution of Plants. 



1727. By the art of man plants may be inured to circumstances foreign to their usual 

 habits. Though plants in general are limited to certain habitations destined for them by 

 nature, yet some are, and probably the greater number may be, inured to climates, soils, 

 and situations, of which they are not indigenous. The means used are acclimating and 

 culture. 



1728. Acclimating seems to be most easily effected in going from a hot to a cold 

 climate particularly with herbaceous plants. Because it often happens that the frosts of 

 winter are accompanied with snow, which shelters the plant from the inclemency of the 

 atmosphere till the return of spring. Trees and shrubs, on the contrary, are acclimated 

 with more difficulty, because they cannot be so easily sheltered from the colds, owing to 

 the greater length of their stems and branches. The acclimating or naturalisation of 

 vegetables is to be attempted by two modes : by sowing the seeds of successive genera- 

 tions, and by the difference of temperature produced by different aspects. The former 

 is well exemplified in the case of the rice-plant which is grown in Germany, from seeds 

 raised there, while if seeds from its native country, India, are used they will not vegetate 

 [Sir J. Banks, in Hort. Trans, vol. i.) ; and the latter in the sloping banks of Professor 

 Thouin of Paris, as described by Girardin. [Physiologie Vegetale, vol. i.) Some plants 

 seem to have the capacity of vegetating in almost all climes, or of naturalising themselves 

 in almost any. This is particularly the case with the domestic esculents, such as cab- 

 bages, potatoes, and carrots. [Dialogues on Botany, p. 411.) 



1729. Domesticated plants. " Some plants," Humboldt observes " which constitute 

 the object of gardening and of agriculture, have time out of mind accompanied man 

 from one end of the globe to the other. In Europe, the vine followed the Greeks; the 

 wheat, the Romans; and the cotton, the Arabs. In America the Tultiques carried 

 with them the maize ; and the potatoe and quinoa {Chenopodium quinoa, of which the 

 seeds are used,) are found wherever have migrated the ancient Condinamarea. The 

 migration of these plants is evident ; but their first country is as little known as that of 

 the different races of men, which have been found in all parts of the globe from the ear- 

 liest traditions." {Geogtaphie des Plantes, p. 25.) 



1730. The general eff'ect of culture on plants is that of enlarging all their parts ; but it 

 often also alters the qualities, forms, and colors : it never, however, alters their pri- 

 mitive structure. " The potatoe," as Humboldt observes, " cultivated in Chili, at 

 nearly twelve thousand feet above the level of the sea, carries the same flower as in 

 Siberia." 



1731. The culinary vegetables of our gardens, compared with the same species in their 

 wild state, afford striking proofs of the influence of culture on botli the magnitude and 

 qualities of plants. Nothing in regard to magnitude is more remarkable than in the case 

 of the Brassica tribe ; and nothing, in respect to quality, exceeds the change effected on 

 the celery and carrot. 



1732. The influence of culture on fruits is not less remarkable. The peach, in its wild 

 state in Media, is poisonous, but cultivated in the plains of Ispahan and Egypt, it be- 

 comes one of the most delicious of fruits. The effect of culture on the apple, pear, 

 cherry, plum, and other fruits, is nearly as remarkable ; for not only the fruit and leaves, 

 but the general habits of the tree, are altered in tJiese and other species. The history of 

 the migration of fruit-trees has been commenced by Sickler, in a work (Geschicte, &c.) 

 which Humboldt has praised as equally curious and philosophical. 



1733. The influence of culture on plants of ornament is great in most species. The 

 parts of all plants are enlarged, some are numerically increased, as in the case of double 

 flowers ; and what is most remarkable, even the colors are frequently changed, both in 

 the leaf, flower, and fruit. 



1734. Tlie influence of civilisation and culture^ in increasing the number of plants in a 

 courUry, is very considerable, and operates directly, by introducing new species for cul- 



