Repository: UIHistories Project: Board of Trustees Minutes - 1884 [PAGE 96]

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100 recognized in the herbaria of our country, and nearly or quite uniform under the name quoted. But Schweinitz published this name in 1822 (Syn. Fungi Carol., p. 78), seven years after De Candolle had published the description of a species of Puccinia under the name of P. tanaceti (Flore Franc II, p. 222). Now, it is found that no specific difference can be maintained between these, therefore the latter name must be adopted for the collections made in America as well as for those of Europe.

ORDER

UEEDI^TEJE.

DEBARY.

Parasitic plants of minute size, growing in the tissues of living phanerogams, or, in a few cases, of living vascular cryptogams; mycelium articulated, variously branched, penetrating, or growing between, the cells of the host; spores usually produced by constriction, singly or in chains, from the ends of fertile hyphse (mycelium branches) formed beneath, rarely within the cells of the epidermis which is ultimately ruptured; fruit forms of different kinds, viz.: secidia, spermogonia, uredospores, teleutospores. The Uredinece are parasites and affect a very large number of the species of the higher plants, being found most often upon the leaves, but also in some instances upon the stems and parts of the flower and fruit. Eoots alone are free from their intrusion, and these probably because protected by the soil. The most remarkable thing concerning the Uredinece is their peculiar alternations of fruit forms—"dimorphism," "polymorphism" or "pleomorphism." The teleutospores, the last in the series and usually the only ones surviving the winter, emit upon germination a slender tube called the promycelium. This is never very long or complex in structure, but may be with or without septa, simple or branched. It produces at once, on minute stalks (sterigmata), one to several thin-walled, more or less globular bodies, rich in protoplasm, and known as sporidia. These in turn soon germinate by sending out a little tube which, upon the proper host, penetrates the tissues and forms the mycelium, or vegetative structure of the parasitic plant. Then follow in order, as products of the mycelium, the fruit spores known as spermogonia, secidia, uredospores and teleutospores. The two first are usually produced simultaneously or nearly so on the same infected area of the host; but most often on opposite sides, if of a leaf. In some cases the other fruit forms subsequently develop in the order named, upon the same mycelium; but in others only on a new mycelium produced from the germination of the secidium spores, and either on the same or different host according to the habit of the species. These alternations may be best understood by consulting what is said under the genus Puccinia. But this full series of forms is not found in all the species. Indeed there are comparatively few which are really known to have in their regular course of development all the stages as necessary requirements of growth. In a few instances it is known that species which under some circumstances have this or that form produced,