74 THE PHYSIOLOGY OF PLANTS 



paratively weak solution of nutritive matter, while highly con- 

 centrated solutions are beneficial to Crucifer^B (especially our 

 vegetables), ResedacecB, Cucurbitacea?, Chenopodiacege, &c. 



If we seek for sound guidance from the aspect of the 

 plant as to the amount of concentration which it requires, we 

 may take it as a general rule that plants with leathery leaves, 

 with hard and narrow leaves, and with hard wood, require 

 more dilute solutions than those with large, soft, and ex- 

 panded leaves. The period at which the manure is added is 

 also of considerable importance. During the period of leaf- 

 formation all plants can do with the greatest amount of nutri- 

 tive matter. 



If pot-plants have suffered from over-manuring, the ball of 

 roots should first of all be examined, to see if the latter are 

 decayed. If this is not the case, the surface of the soil should 

 be loosened, the pots should be washed to keep them as porous 

 as possible, and the watering should be reduced, so that a 

 large amount of air can reach the roots. If the plants must 

 have water, add it in such quantity that it escapes by the 

 hole at the bottom of the pot. Pure water only should be 

 used, and the pots should remain in their ordinary position. 

 If, however, the roots be injured by decay, then the plants must 

 be re-potted. After the removal of the decayed parts the plants 

 should be potted in a loose soil in small pots, be given mode- 

 rate bottom heat, a close atmosphere, increased shade, and 

 diminished water supply. If bottom heat is not available, the 

 plants should be entirely screened from the mid-day sun, and 

 during the heat of the day the upper portions of the plant 

 should be kept moist by sprinkling, but the watering of the 

 roots should be reduced to a minimum. The plant must rest 

 as much as possible until the development of new leaves indi- 

 cates the renewal of its activities. Then the patient may be 

 removed to lighter quarters, and the water supplied to the 

 roots may be gradually increased. The efficacy of this treat- 

 ment I have had ample opportunity of testing. 



