Publisher's Synopsis
Excerpt from The Gymnosporangia or Cedar-Apples of the United States
In consequence of the prevalent View with regard to the development of the Uredineae, writers have ceased retaining such genera as Uredo and Aecidium except as receptacles for the forms which have not yet been connected with any definite final form, and on the continent a new nomenclature has arisen which has not as yet been a'dopted by American writers. For the purpose of illustration let us take Puccinia Graminis, the common blight on grass which was minutely studied by De Bary.1 The final form appears as black Spots or lines on the leaves and stems of grasses, and is composed of dark colored, rather thick-walled spores, formed of two more or less conical cells united by their bases and at tached at the lower end to a mycelium. These two-celled spores are called teleutospores and, in the case of Puccmta Graminis, are produced in. The autumn. When left to them selves, they germinate the next spring in the following manner. From each cell is given off one, or occasionally two or three, delicate filaments, which scarcely exceed in length the length of the teleutospore. The upper part of the filament becomes somewhat enlarged, and there are generally formed from two to four cross partitions by which the filaments are divided into two to five cells. The upper cells grow out laterally and bear each a small ovoid cell which readily falls from its attachment. The name given by Tulasne to the ger minating filaments was promycelium, and he called the secondary small ovoid cells sporidia. In the case of Puccinia Graminis, according to De Bary, the sporidia do not grow except on the common barberry, on which plant they produce in the spring or early summer what is popularly called a cluster-cup, or in botanical language an aecidium. The so-called aecid ium is a complex affair. The mycelium from the germinating sporidia produces in spots a swelling and discoloration of the barberry leaves. The spots are more or less of a reddish yellow color, and there soon appears on the upper side of the leaves a number of minute, deep brown pustules called Spermogonia. A section through the spermogonia Shows that they are cavities lined with slender filaments, the tips of which, called spermatia, separate and escape in masses from the Spermogonia. Soon after the appearance of the Spermogonia on the upper side of the leaves, the lower surface swells and bears a number of cups, the aecidia proper. The cups are really formed inside the leaf, and are sacks com posed of a cellular covering or peridium, and orange-colored spores arranged in rows arising from the base of the peridium. When they come to the surface, the peridia rup ture and the Spores readily escape. The aecidial spores germinate upon different grasses, and produce in summer what is called the rust, that is, Spots or lines containing a rusty colored powder. The rust stage is called by botanists the uredo and consists of rather del icate, oval, unicellular spores of an orange-red colour, often called stylospores, attached to a mycelium. Like the aecidial-spores, the uredo-spores easily fall from their attachment, and germinate on grass and produce late in the season the pustules which bear the teleuto Spores already described.
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