Germination, chemical experiments respecting.

The late discoveries in chemistry, have thrown much light on this subject.

In 1793 , M. Humboldt discovered, that simple metallic substances are not favourable to the germination of plants, but that metallic oxyds favour it in proportion to their degree of oxidation.

This led him to search for a substance with which oxygene might be so weakly combined as to be easily separated, and he tried oxygenated muriatic acid gas mixed with water. Cresses (See Lepidium), in this acid shewed germs at the end of fix hours, and in common water at the end of 32 hours.

The action of the acid on the vegetable fibres was announced by a great number of air-bubbles covering the seeds, which did not take place with water till the end of from 30 to 45 min.

These experiments, published in Humboldt's Flora Subterranea Fribergensis, and in his Aphorisms on the Chemical Physiology of Plants, have been repeated by Messrs. Uslar, Plenck, Villdenow and others.

See Dictionaire de Physique, par Gehler . They were made at a temperature of from 12 to 15 of Reaumur.

In 1796, Humboldt made some new experiments, and found that, by joining caloric to oxygen, vegetation was still more accelerated.

He threw equal quantities of the seeds of garden cresses into pure water and oxygenated muriatic acid, at a temperature of 58° F. Cresses germinated in the acid in three hours, but in the water not till the end of 26 hours.

In the muriatic, nitric or sulphuric acid, there was no germ at all: though according to the experiments of M. Candolle, the nitric acid accelerates germination also, when greatly diluted with water.

Prof. Pohl at Dresden caused the seed of a new species of Euphorbia to germinate in oxygenated muriatic acid, though taken from Bocconni's collection of dried plants, 110 or 120 years old.

Jacquin and Van der Schott at Vienna threw into oxygenated muriatic acid all the old seeds, which had been kept 20 or 30 years at the botanical garden, every attempt to produce vegetation in which had proved fruitless, and the greater part of them, even the hardest seeds germinated.

Among these were the yellow bonduc, or nickar tree, (See Guilandina,) the pigeon pea, (See Cytisus,) the Dodonaea Angustifolia, the climbing mimosa, (See Mimosa), and some new species of the Homaea . There are not shewn at Vienna any valuable plants, which are entirely raised by the oxygenated muriatic acid, and are from five to eight inches high.

Humboldt made the clusia rosea to germinate, the seeds of which had been brought from the Bahama islands by Boose, and had resisted every previous effort to make them vegetate.

For this purpose he used a new process, which will be easier for gardeners who cannot procure the oxygenated muriatic acid.

He formed a paste by mixing the seeds with the black oxyd of manganese, and then poured over it the muriatic acid diluted with water, in the proportion of half a cubic inch of the acid to three of water.

The vessel containing this mixture must be covered, but not shut close, lest it should burst.

At the temperature of 95°, the muriatic acid becomes strongly oxydated; the oxygenated muriatic gas which is disengaged passes through the seeds; and during this passage the irritation of the vegetable fibres takes place. Philos. Mag.