Mosses, one of the seven families or classes into which all vegetables are divided by Linnaeus in the Philosophia Botanica. The characteristics of these plants, according to the sexual system, are,

1. Tops, without filaments or threads. 2. The male flower, constituted by the presence of the anthera or tops, placed apart from the female, either on the same or distinct roots. 3. The female flowers deprived of the pistillum, or pointal. 4. The seeds devoid of both lobes (cotyledones), and proper coverings; so that they exhibit the naked embryo.

This tribe of plants, as well as the mushrooms, ferns, and sea-weed, is still imperfectly known. Dillenius, professor of botany at Oxford, was the first who attempted an arrangement of them. In his Catalogus Plantarum circa Gissam published at Francfort in 1719, and afterwards in his Historia Muscorum published at Oxford in 1741, he divides the mosses into 16 genera. This arrangement, however, includes the lichens, some of the fuci, and other plants which belong to very different families. The work in question is, notwithstanding, valuable, in having introduced the knowledge of upwards of 200 plants, which were unknown before Dillenius: it is, besides, of all his works of this kind, the best executed, both for the descriptions and figures, and should serve as a model to such authors as intend to publish in detail the history of any particular family of plants.

Micheli, in a work intitled Nova Plantarum Genera, published at Florence in folio in 1629, divides the mosses into two sections, from the figure and situation of their flowers. These sections comprehend together 16 genera, amongst which are improperly arranged, like those of Dillenius, several of the lichens and other sea-weed.

The discovery of the seeds of the mosses, though made by Dillenius in 1719, is arrogated by Linnaeus to himself, who did not begin to write till 1735.

In Ray's method, the mosses form the third class: in Tournefort's, they constitute a single genus, by the name of muscus, in the first section of the 17th class, which comprehends the mosses, mushrooms, and some of the algae or sea-weed, and is distinguished by the name of aspermae, or plants without seed; the seeds of the mosses not having been detected by Tournefort.

In the sexual system, these plants constitute the second order of the class cryptogamia, which contains all the plants in which the parts of the flower and fruit are wanting, or not conspicuous. This order is subdivided into 11 genera, from the presence or absence of the calyx, which, in these plants, is a veil or cover, like a monk's cowl, that is placed over the male organs, or tops of the stamens, and is denominated calyptra; from the sexes of the plants, which bear male and female flowers, sometimes on the same, sometimes on distinct roots; and from the manner of growth of the female flowers, which are sometimes produced singly, sometimes in bunches or cones. These distinctions are mostly borrowed from Dillenius, whose excellence in developing this part of the vegetable kingdom Linnaeus very readily acknowledges.

Musci, is likewise the name of the 56th order in Linnaeus's Fragments of a Natural Method. See Botany, p. 1317.