PRACTICAL INFERENCES. 121 



must observe for himself whether the plants he wishes to 

 grow are naturally shallow or deep-rooted; whether the 

 roots break up into a dense leash of fine fibres encompass- 

 ing and traversing in all directions the soil within a certain 

 limited area ; or whether, as in the case of lucerne, the 

 " root " consists of a long, thick underground stem, capable 

 of extending itself for many feet, and giving off, within a 

 small extent, only a comparatively small number of fibres. 

 The different forms of roots previously alluded to may be 

 looked on as adaptations to different conditions of the soil, 

 especially in relation to water, and the choice of site and 

 mode of tillage must be governed by circumstances. Leaf* 

 development is thus consequent on root-growth; but, in 

 addition, an adequate supply of moisture and heat and full 

 exposure to light are demanded. The adjustment of these 

 agencies is rarely under the control of the farmer to any- 

 thing like the same extent that it is in the case of the 

 gardener. The gardener can often contrive, for instance, by 

 appropriate modifications of treatment, to keep his plants 

 in a growing condition, and to prevent them from "bolting" 

 into flower, whereas the agriculturist is much more the 

 slave of circumstances. Drought and heat check his crops 

 before their growth is complete, and induce premature de- 

 velopment of fibre, of flower, or of seed. Excessive mois- 

 ture and superfluity of rich food will cause the crops to 

 become too rank in their growth, to develop immature 

 succulent tissue, comparatively devoid of the nutritious 

 secretions in which their value consists, and will check 

 the development of flowers. 



The observant eye of the farmer soon detects the un- 

 healthy state of the crops by the colour of the leaves. If, 

 from any cause, root-action is deficient, or sun-heat and 



