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DECOMPOSITION OF PLANTS.

accomplished by the agency principally of other animals, or animated creatures; so, in the vegetable world, vegetating substances usually effect the entire decomposition for though, in the larger kinds, the high and lofty ones of the forest, insects are often the primary agents, yet other minute substances are commonly found to accelerate or complete the dissolution. Fungi in general, particularly those arranged as sphæria, trichia, peziza, and boletus, appear as the principal and most numerous agents, and we find them almost universally on substances in a certain state of decay, or approximation to it; though there are a few genera of this class which are attached to, and flourish on, living ve getation. The primary decline is possibly occasioned by putrescence of the sap, or defective circulation, and this unhealthy state of the plant affording the suitable. soil for the germination of the parasitic fungus; for there must be an original though inert seed, till these circumstances vivify its principle. By what means the parasite finishes the dissolution is not quite obvious; but of that insidious race the byssi, of which family is the dry-rot (byssus septica), the radicals penetrate like the finest hairs into the substance, and thus destroy the cohesion of the fibres. So do the nidulariæ, many of the agarics, the boleti, and others; and it is not unlikely that this operation is the general principle of action of the whole race, though not so obvious in the minuter kinds. These terminators, many of which present but little character to the naked eye, under the microscope we find to be of various forms, though not always so distinguishable from each other as the flowers of our garden. Some of the genera of plants appear to have distinct agents assigned to them, and the detection and enumeration of them have been carried to considerable extent by some of the foreign naturalists; but, to point out the variety and curious organization of these substances, we will only instance four, to be found on the common plants of the garden or the copse: the laurel, the elm, the sycamore, and the beech.

The laurel (prunus laurocerasus) is not, properly speaking, a deciduous plant, though it casts its leaves

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DECOMPOSITION OF THE SYCAMORE.

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in considerable numbers during the spring and summer seasons. These long resist the common agents of dissolution, like those of the holly, by means of the impenetrable varnish that is spread over them. This, however, wears off, and they decay; but their destruction is at times accelerated by a small excrescent substance, which fixes on the leaf, breaks the surface, and admits humidity. It appears in the form of a small black speck, and, when ripe, discharges a yellow powder from the centre; but as soon as one speck, which is the vessel containing the capsules, has fixed itself on one side of the leaf, a similar one will be found immediately opposite on the other; and hence it is well named by Lamarck the two-fronted uredo (uredo bifrons).* This I believe to be peculiar to the laurel and the holly.

The leaf of the elm in autumn may commonly be observed marked with dark-colored blotches, which are the "plague spot" of its destruction. These leaves remain in large proportions uninjured through the winter months; but when spring arrives, the spots become matured, the surface cracks, and the capsules discharge their seeds. Lamarck names it sphæria xylomoides, but mentions another as a more early observer. At these spots the decay of the leaf generally commences.

Most persons must have observed that the upper surface of the leaves of the sycamore (acer pseudoplatanus) is blotched with dark-colored spots (xyloma acerinum) in autumn. This leaf is detached by the earliest frosts, and falling to the ground the spots commence their operations by corroding away the portions of the leaf that surrounds them, but continue attached themselves, appearing as raised, shining, vermicular lines. This has been mentioned by Lamarck and others, and is only now noticed to point out the vari

* Without close examination, this plant appears to be a uredo; but it is in fact a sphæria. Uredo differs from sphæria chiefly in the vessels not containing the capsules in cells, but loose. Hoffman observes, that both sphæria and uredo discharge pollen from an orifice; but, if the summit of this plant be cut off, the capsules are obvious.

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DECOMPOSITION OF THE BEECH.

ously constituted agents that accomplish the destruction of the foliage of plants.

The bark, the wood, have other deputed powers of destruction, many of which are very beautifully fabricated. To dwell on them would extend too much these remarks, designed rather as observations than details; yet I am tempted to introduce two. The sphæria coryli of Lamarck (peziza coryli) is occasionally to be found in the month of January, and through the winter until April, upon old hazel sticks, and engages our attention by the regularity of its tubercles. The seed, or first principle of production, whatever this may be, by means unknown to us, has been fixed upon the inner bark of the wood. Gently increasing, it bursts its way through the outer bark, which now hangs as a fringe about it; the seed vessels expand, and a dusty substance, being most probably the matter that continues the species, is dispersed around. A singular plant (sphæria faginea?) is found upon the decayed wood of the beech-tree,* in the earlier part of the spring. It appears on the surface of it in little nodules, which, gradually uniting and increasing, form a regular black crust. Upon examination we find, that little round bodies have forced a passage through the outer bark, and enlarged into small round tubes, which ultimately become the conductors of the seminal dust, discharged from round, beaked seed vessels, embedded beneath upon the inner bark. This plant presents us with a very remarkable instance of the attention of nature to the preservation of minute and little observed things; the protection of the seed vessel, and the dissemination, being most particularly and carefully provided for.

These specimens are only individuals among hundreds, which present us with a world of beauty, variety, and wonder. I would not wish it to be understood that it is maintained, by any thing here intimated, that the

* I am uncertain whether this plant has been noticed. Sphæria granulosa of Sowerby, and sp. tentaculata of Batsch, may be it in a young stage of growth; sp. faginea of Lamarck does not accord well with it.

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