1840.] SENATE— No. 36. 83 



The importance of a rotation of crops is explained by a re- 

 cent and curious discovery in vegetation, which striking and 

 satisfactory experiments seem to have verified. The dis- 

 covery, to which I refer, is that of the celebrated botanist 

 De Candolle, in relation to the excrementitious powers and 

 habits of plants. Of the nutriment, which they receive and 

 digest, they exude an inconsumable or innutritive portion by 

 theft roots. This excrementitious matter, is supposed to unfit 

 or poison the soil for a second crop of the same kind, until it is 

 either consumed or neutralized by cultivation. But this very 

 matter may prove nutritious to a different kind of plants. 

 That plants discharge by their roots an excrementitious matter 

 of the kind referred to, careful experiments have placed beyond 

 a doubt ; and it is, in his opinion, for these reasons that one 

 white crop should not succeed another. This matter is un- 

 derstood to be discharged mainly when the seed is formed ; 

 but this point is not conclusively established. It is ascertained 

 that it takes place more by night than by day. 



One consideration ought not to be lost sight of. Wheat 

 should never follow a crop which has not been thoroughly cul- 

 tivated and in the cleanest manner. For this reason it is pro- 

 bable that it has been found to do better after a crop of corn 

 than after a crop of potatoes, for with but few exceptions, noth- 

 ing is more slovenly among us than our cultivation of potatoes. 

 I have seen with chagrin many crops of wheat, which other- 

 wise might have been expected to yield abundantly, completely 

 smothered by a profuse growth of weeds. 



Selection of Seed. — I come next to speak of the selection 

 of seed wheat. More than one hundred and fifty distinct varie- 

 ties have been ascertained, but the cardinal distinctions are few, 

 and may be summed up into the flint and the thin skinned, 

 the bearded and the bald kinds. These seem to be original 

 distinctions ; but the matter of one kind ripening in a shorter 

 time than another is probably tlie effect of selection and cul- 

 tivation. A spring wheat may be changed into a winter grain ; 

 and a winter grain into a spring grain, by careful selection. 

 How much may be accomplished in this way, is well illustra- 



