The laurel (prunus laurocerasus) is not, properly speaking, a deciduous plant, though it casts its leaves 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).[34] 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 pseudo-platanus) 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 variously constituted agents that accomplish the destruction of the foliage of plants.