UPON PLANT-HOUSES. 75 



Now these 2}lant(B aprica: requii'e strong light ; for between 

 the tropics they enjoy it from morning until night, with a most 

 vertical sun ; in a weaker degree beyond the tropics. All night 

 the firmament is clear, and the radiation of heat veiy powerful, 

 especially at places which are void of vegetation. The crowded 

 plants throw a narrow and flickering shadow on each other, and 

 exercise a mutual influence by developing warmth and reflecting 

 light, and thus vei'ify the old saying : Latior una alterius crescit 

 sub umbra. Hence it is that our cultivation is successfully 

 carried on in low houses with oblique windows, on one side, or 

 having them on a pent-roof, in which the heat may be con- 

 veniently regulated and proportioned to the means of introducing 

 light. And hence also the facilities which these structures afford 

 to the observant and experimenting botanist. These buildings 

 recommend themselves besides by their cheapness. On occasions 

 when existing high glass-houses are to be rebuilt, the principle 

 on which to proceed ought to be, to remove low or ground- 

 vegetation altogether. There are besides tropical forest plants 

 of low stature, which, truly speaking, do not belong to the class of 

 ground-plants, and which are cultivated not merely for the sake 

 of their general appearance or habit, but for the sake of their 

 producing flowers and fruit : all such should be removed from the 

 serves cV exhibition, or palm-houses, into the low or forcing-houses. 

 They require that the light and heat should be nicely proportioned, 

 especially during particular periods, and verify the rule : The 

 greater the heat the stronger the light ; which ought by no means 

 to be interpreted, the more light the better. I think I have 

 seen glass-houses into which too great light was admitted during 

 certain periods of rest, such as the state of leaf or flower budding, 

 and which caused a yellowish, attenuated, and somewhat arid 

 appearance among the plants. On the other hand, during the 

 highest leaf-development (e. g. of bulbous plants, Amaryllideee), it 

 is impossible to give too much light with the requisite heat. 



Light and heat are the two powers by which vegetable life is 

 chiefly regulated and modified. Each spring the entire distri- 

 bution of plants over the surface of the globe points at this great 



for these plants, but it never became general, and it soon after declined ; 

 which is the more to be regretted, because their treatment and multipli- 

 cation are so easy. Never shall I forget the display of Hedychiums which 

 the Livex-pool Botanical Garden exhibited under the hands of its excellent 

 gardener, Mr. J. Shepherd, in the days of the illustrious Roscoe. Nothing 

 that I have ever seen could exceed the fragrance and magnificence of the 

 collection at the time in full blossom. 



