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 Dodonæa Angustifolia, the climbing mimoſa, (See Mimosa), and ſome new ſpecies of the Homæa . 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.