54 3/K GARDEN. 



the plants must be educated gradually -to bear it. I have learnt a 

 lesson from observing lady-ferns growing in the full blaze of the 

 sun, and ceterach flourishing on Mount Vesuvius, and on the bare 

 rocks of the Apennines near Florence, under conditions which would 

 have led me to suspect that they would have been killed. 



Light particularly develops the chlorophyl, or green colouring 

 matter ; and without light, vegetables are etiolated or made white. 

 Some culinary vegetables are only used in this white state, such as 

 sea-kale, celery, and endive, which are scarcely eatable when green, 

 from the powerful flavours they contain. 



For the full perfection of all fruit, the fullest exposure to the rays 

 of the sun is necessary, and heat alone without light will not answer 

 the purpose. A pear, peach, nectarine, or strawberry is worthless 

 unless grown under the action of light. 



The solar light is constituted of various rays. The violet or 

 chemical rays, and the red or heat rays, are the two important rays for 

 the horticulturist. Out of doors the preponderance of one ray over 

 another is ever varying, as photographers well know ; but, when we 

 interpose glass between the plant and the sun, we find it desirable 

 to choose glass with a slight green tint, as it is better that chemical 

 rays should fall upon the leaves of the plant, rather than heat rays. 



It is natural to expect that the influence of electricity or mag- 

 netism on plants should ,be considerable. My experiments have been 

 negative upon this point, and we may say that nothing is definitely 

 known up to this time, though it is possible, and even probable, that 

 a plant placed under electric tension xnay have its power of leaf 

 evaporation increased. 



Plants supplied with the necessary materials for growth, and placed 

 in a suitable temperature, and exposed to a proper amount of light, 

 do not grow continually. They grow, they rest ; they grow, and rest 

 again. Rest is as necessary for plants as sleep is for man ; but rest 

 does not mean stagnation, as changes are doubtless still taking place 

 in the internal economy of the plant necessary to its future welfare: 

 but however that may be, no gardener can be successful who does 



