INTRODUCTION. 



The improvements in agricultural science and practice, which have been either dis- 

 covered, or brought more conspicuously into notice, since the publication of the last 

 edition of this Encyclopaedia in 1831, may be thus briefly enumerated. 



1. The functions of the leaves of plants are beginning to be more generally understood ; 

 and hence, also, the importance of allowing sufficient space for their exposure to the sun 

 and air, by wider sowing or planting, by judicious thinning, and by pruning. 



Hence, also, when plants are to be destroyed, this may be effectually done by cutting 

 off their incipient leaves as fast as they appear. In this way ferns and other perennial 

 weeds in pastures may be more easily destroyed than by any other mode ; and the same 

 may be said of weeds growing up from the bottoms of ponds. 



As a proof that the use of leaves was not understood by practical men, and even by 

 the officers of the Highland and Agricultural Society of Scotland, so lately as 1836, we 

 may refer to the Transactions of that body ; in which we find the Society giving a pre- 

 mium for an essay on the destruction of ferns in pastures, to a candidate who recom- 

 mends as the best mode the irrigation of these pastures. The irrigation of pastures on 

 which ferns abound may be considered impracticable in ninety-nine cases out of a 

 hundred. 



2. Growth and maturation in plants are two separate processes, and when either is 

 the main object of culture, the other should be prevented or checked; thus when seeds 

 or fruits are maturing, the elongation of shoots and the production of leaves should he 

 checked, by pinching them off as fast as they appear. Hence the use of topping beans, 

 tobacco, woad, and even potatoes ; not to mention vines, gooseberries, raspberries, 

 peaches, and other garden fruit shrubs and trees. 



3. By preventing the formation of seeds or fruits, more strength is thrown into the 

 plant generally ; and if it is a plant which produces bulbs, tubers, or underground stems, 

 as substitutes for seeds, these will be increased in size. Hence the use of picking ott 

 the blossoms of potatoes. 



4. Plants imbibe nourishment from the soil, chiefly from the points of the fibres at the 

 extremities of their roots. Hence the practice of banking up hedges, beans, potatoes, 

 and other plants in drills, and of watering, stirring the soil, and laying manure close to 

 the stems of trees and plants, is erroneous in principle and often injurious in effect ; 

 by cutting off the fibrils, or, in the case of potatoes, the underground shoots on which 

 the potatoes are formed. In some cases, however, cutting off the extremities of the 

 roots is useful by increasing the number of fibrils, and consequently of the spongioles 

 or mouths by which nourishment is imbibed. 



Hence the Berwickshire practice of tabling hedges so much recommended, and so 

 generally followed by Scotch bailiffs, foresters, and hedgers, is for the most part a 

 waste of labour; unless, indeed, the object be to stunt the growth of the hedge, and 

 prevent its roots from robbing the soil of the adjoining fields. The practice of earthing 

 up turnips was once in vogue, but it is now ascertained to be a certain mode of instantly 

 checking the swelling of the turnip, by the pressure of the soil which is thrown up to it 

 by the plough. 



5. The properties of the fruit of any plant, for example, the gluten of Leguminosa; or 

 wheat, or the starch of potatoes, or the sugar of the beet-root, are more or less diffused 

 over the entire plant : and hence sugar may be made out of the leaves of the beet, as 

 well as the roots, and starch out of the stems of the potato, as well as out of its tubers ; 

 it being understood that the leaves or stems are in a nearly mature state. 



6. The progress of the ripening of seeds and fruits in general goes on in a geometrical 

 ratio, and hence the great nicety required to determine the moment when seeds or fruits 

 should be gathered, which period varies according to the purpose to which the seeds or 

 fruits are to be applied. The last change which takes place in the ripening of wheat 

 is an increase of bran or husk, and a relative diminution of farinaceous matter or flour ; 

 and hence the immense difference in the produce in flour, between that of the grain of 

 a field of wheat cut down at the proper time, and a field of wheat allowed to be over 

 ripe. Too much importance can hardly be attached to this subject. 



7. Running water is found to contain oxygen, potash, carbonic acid gas, and ammo- 

 nia, all which serving as manures for plants, it follows that irrigation, even in < Id 

 climates, is beneficial to grass lands, altogether independently of supplying water as an 

 element of growth, which in cold climates is seldom wanted in that capacity. 



