14 CHEMICAL MANURES. 



ducts ; the second, to their transformation into vegetable tissues and 

 organs. 



Lastly, I add that the mechanism of vegetable nutrition rests en- 

 tirely on these two orders of phenomena, which are both independent 

 and united. 



From the foregoing it results that plants are known to be under 

 the double relation of their composition and manner of formation. 



To complete this general view of vegetable production, I must 

 show you the conditions which regulate its movements, and which, in 

 practice, make their cultivation certain or precarious, expensive or 

 remunerative. 



These conditions are three in number : 



1st. Climate. 



2d. The nature of the soil and the choice and quantity of manures. 



3d. The choice of seed. 



The influence of climates. That is indisputable. "Who has not 

 marked the changes of vegetation in passing from the foot of a moun- 

 tain to its summit ? At the distance of a mile or two we distinctly 

 see the bands of verdure on the inclinations of the Alps, contrasting 

 through thickness and coloring as well as by difference in flora. 



The same thing takes place on a grander scale in going from the 

 equator to the poles. At the equator, vegetation is marked by an 

 appearance of vigor and majesty which strikes a European traveler 

 with admiration. The number of trees, compared to that of the 

 grasses, is greater than in Europe. The trees are also remarkable for 

 height and the size of trunk, as well as for richness and variety of 

 foliage. 



Seventy degrees of latitude from the equator we see only small 

 trees, shrubs and grasses ; and near the pole plants are represented 

 by a few brittle byssus and lichens creeping over the surface of the 

 ground. 



Climate, therefore, exercises a considerable influence on vegetation, 

 and he would be wanting indeed who ignored it in practice. 



"Would it not be folly to cultivate the vine at Dunkirk, maize at 

 Valenciennes, and the olive on the plains of Beauce? These are 

 exaggerations, I know, but under them there is a truth it would be 

 well to remember, that in our day agriculture tends to specializations, 

 and we should always have the climate in our favor. With a free 

 commerce and facility of exchange, each region should create a mo- 

 nopoly of its products in which it may defy competition. 



The English, an enlightened people, understood this long ago: 

 wherever too great moisture of climate made the cultivation of grain 

 unprofitable, they have substituted grasses and herds. 



Among the conditions acting on vegetation we have placed the 

 composition of the soil, and in the same order of ideas the choice of 

 manures in the second rank. 



You know that two fields touching each other may often be of 

 unequal fertility. The cause of these differences is in the presence 

 or absence of certain agents. Add to the one the elements wanting, 

 and it will become m fertile as the other. Under this view, by the 



