GENERIC DISTRIBUTION OF FOLIOSE MUSCI.
Before the timc of Dillenius, no attempts seem to have been made to divide mosses into genera. Pharmaceutical writers, indeed, had long been accustomed to name Polytrichum commune, Adiantum aureum majus ; and Funaria hygrometrica, Adiantum aureum minus. But these were mere individual appellations for two solitary plants used in medicine ; and muscus, with some phrase descriptive of the particular species, or some reference to a previous author, was used as a generic name in common to the whole family. Dillenins saw the incon venience of this, and remedied it by the institution of gcneta. But taking the term Musci in an extended sense, he admitted into his admirable Historia Muscorum many plants having extremely little affinity to those de scribed in this article. By the name of moss," says Dillenius, I designate a class of inferior plants, of which the genera, being more imperfect, consist either of parts that are simple and uniform, being destitute equally of flower and fruit ; or they are endowed with diversity of parts, and bear something instead of flowers and ft uit, which answers to them." With this latitude of definition, he was enabled to include in his Bistoria some of the minute fungi; a great many Algx, such as the whole tribe of Confervx ; tnany Ulvw, and some Tremellx, comprehending both under the generic name Tremella; the whole tribe of lichens, under the generic names Usnea, Coralloides, and Lichenoides ; besides Lycopoclium, (assigned to the Filices of some later au thors,) divided into the three Dillenian genera, Lycopo dium, Selaginoides, and Lycopodiu:des. His other genera belong either to the foliose or the hepatic rausci. 'Ihe following six Dillenian genera contain all the foliose musci, which he has described and figured.
The two different sorts of powdery heads ascribed by Dillenius to Mniurn, and on account of which he has placed it in a division by itself, are the male and female fructification. The calyptra of Sphagnum, at least that
part of it raised by the capsule, is very fugacious, and had escaped the notice of Dillenius ; hence he errone ously characterises the genus by the want of a calyptra. The capsules of Fontinalis are now well known not to be sessile, though the fruitstalk is short ; and the scaly in volucrum, at the base of the fruitstalks of Hypnum, is exactly analogous to the (6 sheath or calyx" of Fonti nalis.
This, as the first attempt at systematic arrangement of musci, is far from destitute of merit ; but it is the ad mirable descriptions and figures of the Historia Masco rum which constitute its chief value.
Porella, or, as it is called in The Conslzectus, Poronia, is placed in this system between Lycopodium and Se laginoides ; hence it would appear that it was consider ed by Dillenius as having more affinity to the Lycopo dincx than to the musci proper. And certainly, ab stracting from the difference of textute, there is a very considerable resemblance in habit between some of the bifarious leaved Lycopodia, and of the bifariuus leaved Jungermannix.
Several plants at e introduced which are not referred to any genus. Among these is Buxbaumia aphylla, which has no other name than the descriptive one ori ginally given to it hy Buxbauni himself, " Muscus ex iguus aphyllos, capitulo crasso and bivalvi." Diphys cum foliosum is reckoned a Sphagnum.
Linneus' System of Foliose Musei, (from the 13th edit. of the Syst. A'at.—Vindob. 1767-70.) 1. Lycopodium, antlicra bivalve, sessile ; no calyptra.
2. Porella, anthera mutilocular, penetrated by many pores ; with. out operculum and calyptra.
3. Sphagnum, anthera operculatc; the mouth smooth ; no calyptra. Phascum, anthem °percolate ; mouth ciliated; calyptra minute.
5. Fontinalis, anthera operculate ; calyptra sessile, enclosed in a perichzetium.
6. Buxbaurnia, anthera operculate, membranaccous on the one side ; calyptra caducous ; a little bag of pullen within the opereulum.