2. Of Genana, or Buds.
In the genus Jungerrnannia, these appear to occur on only a few species. In J. minutissima, J. calyptrifolia, and some other minute species, they seem to be pro duced on the stems ; in J. complanata, on the margins of the leaves; in J. furcata on the extremity of the frond ; and in J. Blasia within proper tubular receptacles These receptacles were formerly considered as the fruit of this plant, which was accordingly, from the time of Linnxus downwards, till the publication of the last number of Dr. Hooker's admirable monograph uf the British Junger mannix, considered as of a distinct genus termed Blasia. Specimens of this plantovith capsules, had been gather ed long before by Mr. Dickson, on the shores of Loch Tay, who took it for a new Jungermannia. About the same time that these were communicated to Dr. Hooker, specimens without capsules 1,vere sent to him by Swartz. The marginal gemmx in both immediately attracted his attention. Mr. Lyell found the plant at Kinnordy, and having watched its progress, he obtained specimens with young fruit, not )et burst from the the calyptra, and soon after, the same gentleman sent from Ambleside a specimen with the capsule burst from the frond. And Dr. Taylor, now of Cork, found ripe capsules on the mountains at Loch Bray, in 'March, 1814. Thus was the genus Blasia erased from among vegetables, and the species formerly known by the name of Blasia pusilla became Jungermannia Blasia.
In structure, the gernmx of Jungermannix resemble the leaves of the species which produce them. Thcy vary in form, being spherical in J. Blasia, J. ealyptri folia, and some others, and in J. complanata and J. fur cata, somewhat oblong. Those ofJ. Blasia are furnished with roots, even before their escape from the proper re ceptacle, and in that species, as well as in J. furcata, their progress towards perfect fronds may be easily traced.
The gemmx of Marchantia are contained within pro per cup-shaped receptacles. These receptacles appear at first as minute slightly elevated spots, but after having increased somewhat in size, they open, and disclose a number of oblong substances, tapering towards both ex tremities, each of which, in clue time, falls out of the re ceptacle, and in favourable circumstances, becomes a perfect plant. On the sterile fronds of /1,1. polymorpha, these cup-shaped receptacles of gemmx are often very numerous. No gemmx have been hitherto detected on any other of the hepatic musci.
Generic Distribution of the Hepatic or Deoperculate Mosses.
The only alterations which have taken place in the generic distribution of this family since the time of Lin nxus, are, the blotting from the list the genus Blasia, as already mentioned under the article Genimx, a late alteration, and the discovery, also recent, of the genus Monoclea. Indeed, with these exceptions, and the very important one of the discovery of many new species of Jungermannia, the hepatic mosses remain in a state very little different from that in which they were left by Dille nius and Micheli.
I. Jungermannia. No common receptacle of the Fruit. Capsule quadrivalve, seated on a fruitstalk longer than the calyx. No columella.
This very extensive genus contains no fewer than 81 British species ; and 42 rare foreign ones, of which 32 had not been previously published, have been figured and described by Dr. Hooker in the Musci Exotici. The genus is divided into piimary sections, according as the species are leafy or frondose. The leafy species are subdivided into such as have no stipules, and such as are furnished with these appendages. The exstipulated spe cies are again subdivided, according to the insertion of the leaves; whether it be (1) multifariously, or indiffe rently, on all sides of the stem, as in J. julacea ; or (2) bifariously, on two opposite sides of the stem only. This section, containing many species, has them arranged un der the heads, (a) leaves undivided, as in J. asplenioides; (b) leaves emarginate or bifid, the segments equal; as in J. emarginata, J. bicuspidata ; (c) leaves divided into three or four equal segments, as in J. pusilla, J. capi tata ; (d) leaves bifid, the segments unequal, and dou bled ; as in J. nemorosa, J. complanata. The stipulate species are subdivided, (I) into such as have the leaves entire, or with a few scattered notches ; as in J. ano mala, J. Trichomanis ; (2) such as have the leaves di vided into two or three equal segments ; as in J. biden tata, J. trilobata ; (3) such as have the leaves bifid, the segments unequal, and folded on each other ; and this section is subdivided into (a) species having the lower, or smaller segment plain ; as in J. platyphylla; (b) hav ing the lower or smaller segment involute, as in J. ca lyptrifolia ; (c) having the lower or smaller segment saccate, as in J. flutchinsix, J. Tamarisci.