686 



HISTORY OF THE VEGETABLE KINGDOM. 



"colourable principle," or cliromogen of Dr. 

 Hope, is readily extracted Ly water, and the 

 colourless infusion wliicli is thus formed becomes 

 red on tlie addition of an acid, and green on the 

 addition of an alkali. If a neutral salt be dis- 

 solved in this infusion it still remains colour- 

 less; but, if this salt bo decomposed by electri- 

 cal agency, then the acid and alkaline ingredi- 

 ents, being separated, at once produce their red 

 and green coloure. Now, if Ave suppose the 

 carbonic acid gas, which enters the jjarenchjine 

 of the leaves, to be attracted by, and to combine 

 with, the alkaline matter which is so abundant 

 in those organs, it may there form a neutral salt, 

 and whilst this neutral state continues, the leaf 

 will remain colourless; but if the chemical rays 

 of light, acting like electricity in the exami)le 

 before given, decompose this carbonate, and 

 cause the expulsion of its acid ingredient, then 

 the alkali, becoming predominant, will produce 

 its usual effect on the xanthogen of the leaf, 

 and its chromule will in consequence be ren- 

 dered green. In order to maintain this green 

 colour in the leaf, the action of light on its 

 saline ingredients must be regarded as in con- 

 tinual operation; and hence its exclusion, by 

 suspending that action, is followed by a gradual 

 loss of colour; and, as the carbonic acid gas is 

 no longer decomposed, the leaf at the same time 

 ceases to afford oxygen gas. The colouration of 

 the leaf, therefore, is not immediately due to the 

 evolution of oxygen, nor even to the subtrac- 

 tion of carbonic acid, but to the predominance 

 of alkaline matter which that subtraction of 

 acid occasions; consequently, the verdure suc- 

 ceeds to the decomposition of the acid, the evi- 

 dence of which is afforded by the expulsion of 

 oxygen gas. Hence, to speak correctly, we can- 

 not so properly say that the green leaf affords 

 oxygen, as that it becomes green when that gas 

 is expelled; and thus it is, that the decomposi- 

 tion of carbonic acid by the agency of light gives 

 rise, at once, to the evolution of oxygen gas, 

 and the formation of the green colour in plants. 

 The invention of Mr Ward is practicable on 

 the simplest scale, and may be adopted, at a 

 trifling expense, liy any person. A bell glass or 

 crystal bottle, with the bottom cut away, and 

 fitted over a wooden box, or placed over a com- 

 mon flower pot, will answer perfectly well. 

 And thus delicate j)lants may be preserved in 

 perfection. Succulent j)lants, or those that 

 delight in a moist atmosphere, will succeed best, 

 while those plants which flourish in a dry soil 

 and air are apt to deteriorate. The growth of 

 minute fungi, too, from the close damp atmo- 

 sphere, also affects the health of the plants. 

 Boxes of common wood, with glass above, have 

 been constructed, for the transportation of living 

 plants from distant countries. This plan, there- 

 fore, may be practiseil to any extent, or adaiited 



to any scale of expense, which the individu;il 

 may find it either convenient or desirable to 

 employ. When once fitted up, the apparatus, 

 be it either small or large, requires scarcely any 

 farther care or attendance. No fresh watering 

 or airing is at any time required ; nor is any 

 inconvenience experienced from dust and litter, 

 which often render the ordinary mode of keeping 

 plants in well-furnished apartments objectionable 

 and troublesome. Farther, as the plants in this 

 ajiparatus are shut off from all communication 

 with the external air, no apprehension of their 

 injuring the atmosphere, even of close rooms, 

 can be reasonably entertained. The only con- 

 dition, in regard to attendance, that claims 

 observance, is an occasional exposure to light, 

 perhaps for a short period only on days of sun- 

 shine, and for a longer one when the light is 

 more feeble. These are advantages which render 

 the method easily practicable by persons of 

 every class ; and will enable those who are con- 

 demned to live in a smoky atmosphere to refresh 

 their sight with specimens of healthy vegetation 

 within their own abodes, although the district 

 around them should exhibit only the sickly and 

 stunted forms of vegetable existence. 



The celebrated Franklin, who looked at every 

 thing with the eye of a philosopher, and sought 

 to turn to some useful purpose every observation 

 which he made, in recording the reviviscence of 

 some common flies which had made a voyage 

 from Virginia to England in a bottle of Madeira 

 wine, goes on to state that a plant with its 

 flowers f^ides and dies if exposed to the air with- 

 out having its roots plunged in a humid soil, 

 from which it may draw moisture to supply the 

 waste of that which it exhales, and which is 

 continually carried off by the air. Perhaps, he 

 adds, if it were buried in quicksilver it might 

 preserve for a considerable time its vegetable 

 life ; and, if this be the case, it might prove a 

 commodious method of transporting from distant 

 countries those delicate plants which are unable 

 to sustain the inclemency of the weather at sea. 



The ingenious suggestion of the American 

 jihilosoiiher has been happily realised in practice 

 by Mr Ward, in a way much more simple and 

 efficient than that which Franklin proposed. 

 By its means, the rarest and most delicate plants 

 have been transported to and from the most 

 distant countries, with little or no trouble in 

 i-cgard to attendance, and scarcely any risk of 

 suffering from the inclemency of the weather at 

 sea. He lias thereby conferred on the botanist 

 and horticulturist benefits which no researches 

 of travellers, however successful, nor expenditure 

 of money, liowever great, could have enabled 

 them otherwise to procure. Instead of simple 

 descriptions, or dried specimens, or fine pictures 

 of foreign plants, they can now fix their eyes on 

 living specimens retaining their native freshness 



