278 SCIENCE OF AGRICULTURE. Part II. 



or preservation of living specimens of these plants, therefore, in our green-houses and 

 stoves, is an entertainment at once rational and useful ; as many species at length become 

 acclimated, and some even naturalised ; and uses may in time be discovered for such as 

 are now merely looked on as objects of curiosity. ]3ut that they contribute to elegant 

 enjoyment, it is quite enough to justify much more than all the care that is taken to ob- 

 tain and preserve them ; for what is life when it does not exceed mere obedience to the 

 animal instincts? 



1821. With respect to the native habitations of the exotic part of the British Hortus, 

 little can be advanced with certainty. In general it would appear that moist and mo- 

 derately warm climates, and irregular surfaces, are most prolific in species ; and, judging 

 of the whole world from Europe, we should venture to consider half the species of plants 

 in existence as growing in soft and rather moist grounds, whether low or elevated. The 

 soil of surfaces constantly moist, or inclining to be moist, whether watered from the at- 

 mosphere or from subterraneous sources, is generally found to be minutely divided, and 

 of a black vegetable or peaty nature. Immense tracts in Russia and America are of 

 this description, and, even when dry, resist evaporation better than any other. In such 

 soils, the roots of plants are generally small and finely divided, as those of the heaths, 

 most bog plants, and nearly all the American shrubs. The next sort of habitation most 

 prolifi-c in species, appears to us to be arenaceous soils in temperate climates, and in pro- 

 portion to their moisture. Here the roots of plants are also small, but less so than in 

 soils of the former description. On rocky and calcareous soils the roots of plants are 

 generally strong and woody, or at least long and penetrating. In clayey habitations, 

 exclusive of the alluvial deposits of rivers, few plants are found, and these generally 

 grasses, strong fibrous-rooted herbaceous plants, or tap-rooted trees. Such at least is 

 the amount of our generalisations ; but as our observation has been limited to Europe, 

 and does not even extend to the whole of it, those who have visited Africa and Asia are 

 much more capable of illustrating the subject. One conclusion, we think, the cultivator 

 is fully entitled to draw, that the greater number of plants, native or foreign, will thrive 

 best in light soil, such as a mixture of soft, black, vegetable mould or peat and fine sand 

 kept moderately moist ; and that on receiving unknown plants or seeds, of the native 

 sites of which he is ignorant, he will err on the safe side by placing them in such soils 

 rather than in any other ; avoiding, most of all, clayey and highly manured soils, as only 

 fit for certain kinds of plants constitutionally robust, or suited to become monstrous by 

 culture. 



1822. The Hortus Britannicus of 1829 contains nearly 30,000 species and varieties, 

 and the Purchasable Flora of Britain of the same year, contains at least 1000 species and 

 varieties, more than it did in the year 1818 when the above estimate was formed; but 

 the relative proportions of the distribution cannot be materially different now from what 

 they were then, for which reason we have not deemed it requisite to go a second time 

 through the labour of enumeration, for the sake of a result which is by no means essential 

 to a work like the present. 



Chap. VII. 

 Origin and Principles of Culture, as derived from the Study of Vegetables. 



1 823. The final object of all the sciences is their application to purposes subservient to 

 the wants and desires of men. The study of the vegetable kingdom is one of the most 

 important in this point of view, as directly subservient to the arts which supply food, 

 clothing, and medicine ; and indirectly to those which supply houses, machines for con- 

 veying us by land or by water, and in short almost every comfort and luxury. Without 

 the aid of the vegetable kingdom, few mineral bodies would be employed in the arts, 

 and the great majority of animals, whether used by man as labourers, or as food, could 

 not live. 



1824. Agriculture and gardening Sire the two avis vfhich. embrace the whole business 

 of cultivating vegetables, to whatever purpose they are applied by civilised man. 

 Their fundamental principles, as arts of culture, are the same ; they are for the most 

 part suggested by nature, and explained by vegetable chemistry and physiology 

 (Chap. III. and IV.); and most of them have been put in practice by man for 

 an unknown length of time, without much reference to principles. All that is neces- 

 saiy, therefore, for effecting this branch of culture, is to imitate the habitation, and to 

 propagate. This is, or ought to be, the case, wherever plants are grown for medical or 

 botanical purposes, as in herb and botanic gardens. Nature is here imitated as exactly 

 as possible, and the results are productions resembling, as nearly as possible, those of 

 nature. 



