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"It will be enough if, after having led the way on a new territory of investigation, we shall select one or two out of the goodly number of instances, as specimens of the richness and fertility of the land."-CHALMER'S BRIDGEWATER TREATISE, 2—74.

CHAPTER VI.

ON THE PROBABLE FUTURE APPLICATIONS OF THE

PRECEDING FACTS.

The application of the closed cases to the illustration of physiological and pathological Botany must be sufficiently obvious to all who are interested in such enquiries. In most of the experiments which have hitherto been undertaken by vegetable physiologists, the results have been rendered liable to some doubt, in consequence of the fancied necessity for the open exposure of plants to air ; whereas now the utmost certainty can be obtained. I will content myself with specifying a few of the more important instances, in which the close method of growing plants will be found of practical utility.

1. Observations strictly comparative can now be made on the effects of different soils, manures, &c., in cases divided into several compartments, each compartment being filled with different soils, but with the same plants.

2. To determine the powers possessed by plants of absorbing and selecting various substances by their roots.

3. To ascertain the existence and nature of the deleterious excretions from the roots ;— the poisonous character of these excretions, if they exist, being rendered very

problematical by the circumstance of plants in a state of nature occupying the same situations for ages.

4. To prove the effects of poisons upon plants.

5. To test the influence of light in protecting plants from the effects of low temperatures. This can easily be proved by filling a case with specimens of one plant, and by darkening portions of the glass.

In the severe winter which occurred three or four years ago, the noble plant of Araucaria excelsa in the Pinetum at Dropmore was killed. I believe that the plant would not have suffered had light been admitted through the covering which protected it from the cold; and this could easily have been effected by means of melon-lights, &c.

6. To determine various important points respecting those numerous and highly interesting tribes of plants, which, from their extreme minuteness or fugacious nature, have hitherto almost eluded observation, but which the botanist in his study will now be enabled to watch, microscopically if required, during the whole period of their growth. To give an instance:- I had been struck with the published accounts of the extraordinary growth of Phallus foetidus, which was said to attain a height of four or five inches in as many hours. I procured three or four specimens in an undeveloped state and placed them in a small glazed case. All but one grew during my temporary absence from home. I was determined not to lose sight of the last specimen ; and observing one evening that there was a small rent in the volva, indicating the approaching development of the plant, I watched it all night, and at eight in the morning the summit of the pileus began to push through the jelly-like matter with which it was surrounded. In the course of twenty-five minutes it

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shot up three inches, and attained its full elevation of four inches in one hour and a half. The entire life of the Phallus was four days. Extraordinary as this may appear I believe this rapidity of development to be surpassed by other fungi, as I was informed by Lady Arden, who has paid great attention to the species of this family, of which she has made numerous exquisite drawings, that the lives of some were so brief as scarcely to allow of sufficient time to finish her representations. Marvellous are the accounts of the rapid growth of cells in the fungi ; but, in the above instance, it cannot for a moment be imagined that there was any increase in the number of cells, but merely an elongation of the erectile tissue of the plant. Great confusion likewise exists in the determination of the genera and species of this family. Out of one species, according to Fries,* no less than eight genera have been formed, in consequence of this species being seen in different situations and states of growth.

Lastly, I believe that by means of these cases the scientific naturalist will be assisted in exploring that debatable ground on the confines of the animal and vegetable kingdoms, where in our present state of ignorance, it is often impossible to determine the point at which the one ends or the other begins.

I shall conclude my little work with pointing out the application of the principle to animals and to man; an application far outweighing in importance all that has

* This author asserts that out of mere degenerations or imperfect states of Thelephora sulphurea, the following genera, all of which he has identified by means of unquestionable evidence, have been constructed, viz. — Athelia of Persoon, Ozonium of Persoon, Himantia of Persoon, Sporotrichum of Kunze, Alytosporium of Link, Xylostroma, Racodium of Persoon, Ceratonema of Persoon, and some others.—Lindley's Introd.

hitherto been done. In my report to the meeting of the British Association at Liverpool, in 1838, I directed the attention of the members to this subject, at the same time expressing my conviction that a great number of animals would live and thrive under the same plan of treatment which had proved so successful with plants. A little reflection will convince us that this idea is not so visionary as it might appear at first sight. It has now been proved by numerous and long-continued experiments, that the air of London, if duly sifted, is perfectly fitted for the respiration of all plants, even of those with the most delicate leaves, such as the Trichomanes speciosum, which may in fact be considered a test plant as regards the purity of the air. Now this same condition of the atmosphere, so essential to the well-being and even the existence of such plants, we have it in our power to obtain in large towns; and by warming and moistening the air we can in fact closely imitate any climate upon the face of the earth. It cannot be denied that in a pure and properly regulated atmosphere we possess a remedial means of the highest order for many of the ills that flesh is heir to; and every medical man knows well, by painful experience, how numerous are the diseases which, setting at nought his skill and his remedies, would yield at once to the renovating influence of pure air. The difficulty to be overcome would be the removal or neutralization of the carbonic acid given out by animals; but this in the present state of science could easily be effected, either by ventilators or by the growth of plants in connexion with the air of the room, so that the animal and vegetable respirations might counterbalance each other. The volume of the air with the quantity of vegetable matter required, as compared

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