14 SPECIAL HABITS OF PLANTS, 



6. Habits and analogies of the species of plants on which 

 experiments are to be made, and of their several varieties. 



But a knowledge of the special habits and analogies of par- 

 ticular species of plants, and of their several varieties the soils 

 on which they prefer to grow the diseases to which they are 

 subject the enemies, animal and vegetable, by which they are 

 liable to be attacked, these things are not less important to 

 the suggester of experiments than a knowledge of their general 

 physiological and chemical functions. 



Chemistry, from the mouths of some of its more hasty or 

 more ardent cultivators, has promised to make any plant grow 

 luxuriantly, and at will, upon any soil, provided only that it be 

 suited to the prevailing climate. But such promises are mere 

 idle boasting, and argue much ignorance on the part of those 

 who venture to make them. Even chemistry, with all her 

 power, must bend to the constitution and natural habits of a 

 plant. Thus 



1. The oat and the red clover love a firm and stiff soil 

 a natural habit, which chemistry cannot hope to change. On 

 some soils the Tartary oat yields heavy crops, while, on the 

 same soil, the more valuable potato oat refuses a remunerative 

 return. Where other varieties of oats grow sound, the Hope- 

 ton oat is subject to a disease called sedge or tulip root, which 

 is gradually driving it out of cultivation. I do not know 

 whether these qualities of the potato and Hopeton oats be 

 within the dominion of mechanical or of chemical causes. 



2. Wheat. Winter wheat fails in many places where spring 

 wheat is found to do well. Such a result has been observed in 

 the island of Islay, where so many improvements have in late 

 years been made by Mr Campbell of Islay. Is chemistry or 

 climate, or the special constitution of the variety of wheat, or 

 the mechanical condition of the soil, to blame for this ? and 

 which of these causes has most to do with the capability of this 

 or that field to grow white or red wheat, or with the greater 

 productiveness of this than that variety of seed on similar soils?* 



* For a statement or classification of the differences that occur among 

 varieties of wheat, see Col. le Couteur'R book on wheat, p. 79. 



