ON ROTATION OF CROPS. 175 



yet been made relative to it. Mr. Brookman has raised 

 some plants in sand, and ascertained that they exuded 

 by the roots small drops during the night, which there is 

 reason to suppose was the object in research ; but experi- 

 ment has not yet been pushed far enough fully to verify it. 



Caroline. It appears to me to explain the theory of 

 assolement so well, Mrs. B., that I feel strongly inclined 

 to put my faith in it. How perfectly it accounts for the 

 advantages derived from cultivating leguminous and gra- 

 miniferous crops in succession, the exudations of the one 

 being exactly the nutriment which the other requires. 



Mrs. B. I am so much inclined to agree with you in 

 opinion, that I shall venture to draw conclusions from it, 

 as if the theory were established ; cautioning you, howev- 

 er, to bear in mind, that until it has been further investi- 

 gated, it must be considered as little more than hypothetical. 



You must besides remember that it is manure which 

 affords the grand store of provisions equally good for plants 

 of every description. If, in addition to the exudations of 

 leguminous plants, you plough in the crop itself, the suc- 

 ceeding crop of corn will be considerably improved. 



Emily. Supposing you were to plough in a crop of 

 young rye, could you not the following year sow wheat 

 with advantage ? for the rye would have had but little time 

 to deteriorate the soil by its exudations, and afford much 

 manure by the fermentation of its own substance. i 



Mrs. B. I do not know that the trial has ever been 

 made ; but it would certainly succeed better than if you 

 were to reap the rye when ripe, and afterwards sow wheat: 

 for, in this case, the rye would have given to the soil the 

 whole of its exudation, and little or none of its own sub- 

 stance. ; 



Caroline. May it not be objected to this theory that Na- 

 ture does not raise plants of different families in succesion ? 

 The seeds of the parent-plant fall to the ground annually, 

 and produce other individuals of the same species, and on 

 the same spot, for centuries ; and yet that spot must be 



959. What was done by Mr, Brookman 1 960. For what does 

 Caroline say it will account'? 961. Of what does Mrs. B. caution 

 Caroline 1 ? 962. What does she tell her must be remembered'? 963. 

 What answer is given to the question If a crop of young rye were 

 ploughed in, what would be the effect upon the growth of wheat the fol- 

 lowing year*? 964. What question does Caroline then ask on the same 

 (subject, and what illustration of her meaning does she givel 



