10 



SCIENCE OF GARDENING. 



proportion of heat, which is necessary to their vitality; and 

 soils are in winter usually warmer than the air. It is in 

 preventing this heat from flying off into the air, and not 

 in imparting fresh heat, that the true philosophy of 

 shelter consists, 



2. — Light. 



Without light, heat would merely expand the parts of 

 plants : light must elaborate the sap into pulp. Plants 

 that are excluded from light become drawn and weak, as 

 under the shade of trees or walls, and in dwelling-rooms. 

 Even grass, which is endowed with such a wonderful power 

 of life, dies under the thick shade of trees. Plants natu- 

 rally turn to the light, and grow towards it, their tissues 

 becoming more elaborated and contracted on the side from 

 which light is supj)lied : hence their feebleness and one- 

 sidedness. If plants be placed in a warm cellar, where 

 light is only supplied from a single aperture, they will 

 always grow in that direction if the rays can reach them. 



There can be no fruit or flowers without light, because 

 none of the parts of plants can be fully and properly 

 matured ; and the flower or fruit-bearing process is the 

 result of the last stage of maturity. Greenness, and all 

 high colours, are the result of light ; leaves have only a 

 sickly yellow hue without it. Sut it must be remembered 

 that flowers, once developed, will fade sooner when sub- 

 jected to strong light, which will rather throw them into 

 fruit. When flowers, therefore, and not fruits, are desired, 

 a little shading, after the first blossoms have expanded, 

 will prolong their beauty. 



The exclusion of light produces hlancJiingy as in the 

 familiar cases of lettuce, endive, and celery ; but it gives 

 additional succulence, and crispness, and tenderness, as 

 with the sea-kale. All vegetables, therefore, that are used 

 for their juiciness, or eaten raw as salads, or in which 

 much fibre Would be a defect, should be grown quickly, 

 with plenty of warmth, but comparatively less light. 



Want of light is often the real cause of evils which are 

 popularly ascribed to want of air, though both combined 

 may occasionally be acting. Light may, however, be pre- 

 judicial to plants in certain stages, as after fresh planting 



