548 HEPATIC^E. 



776), which, when it falls off, shows the mouth of the urn either naked 

 or crowned with a peristome (sreji, around, and cropa,, mouth), con- 

 sisting of one or more rows of teeth (in number, four, or a multiple of 

 four), distinct, or united in various ways (fig. 776 p). In the centre of 

 the theca is a columella (fig. 777 c), and the bag formed between it and 

 the parietes of the theca, contains spherical cells called spores, each 

 of which divides into four small spores or sporules, the germinating 

 bodies (fig. 777). In some cases the operculum remains persistent 

 and the theca opens by four valves. At the base of the theca there 

 is occasionally a fleshy protuberance at one side called a struma, or a 

 swelling of the seta called an apophysis (dTroQvon;, excrescence), (fig. 

 777 a). The calyptra is sometimes split on one side (dimidiate), at 

 other times it is entire (fig. 775 c) or split into short clefts all round 

 its base (mitriform). Between the teeth of the peristome and the edge 

 of the theca, an elastic ring or annulus is formed; and occasionally a 

 horizontal septum or epiphragm ((ppxy^oe,, a partition) extends across 

 the mouth of the theca3. The setas are sometimes twisted, and so are 

 the teeth of the peristome. Mosses are either erect or creeping, ter- 

 restrial or aquatic plants found in all moist countries, extending from 

 the arctic to the antarctic regions. They abound most in temperate 

 climates. They are among the first plants which appear on newly- 

 formed islands. In speaking of the morphology of mosses, Lindley 

 states that the calyptra may be considered as a convolute leaf, the 

 operculum another, the peristome one or more whorls of minute flat 

 leaves, and the theca itself as the excavated distended apex of the seta. 

 I have a specimen of Tortula fallax, which I received from the late 

 Mr. E. Quekett, in which leaves appear at the top of the seta in place 

 of the spore-case. 



1115. Mosses have been divided according as their seta is terminal 

 (acrocarpi, xg, summit, and x.x^o;, fruit), or lateral (pleurocarpi, 

 wfovpx, side), according as the operculum is adherent or not, and 

 according as the mouth of the theca is naked, or has a single or 

 double peristome. Divisions have also been adopted, founded on 

 the position of the antheridia and pistillidia, &c. Lindley separates 

 Andraja from true Mosses, on account of its spore-case opening by 

 four valves. According to him there are 46 known genera, and up- 

 wards of 1100 species. Examples Andrsea, Phascum, Gymnostomum, 

 Splachnum, Orthotrichum, Dicranum, Bryum, Funaria, Polytrichum, 

 Hypnum, Sphagnum. 



1116. Order 217. Hepatic*;, the Liverwort Family. Plants 

 having an axis which either bears cellular leaves (fig. 778), or is leaf- 

 less and is bordered by a membranous expansion or thallus. Stomata 

 are found in the epidermis of some. The reproductive organs are 

 1. Antheridia, which are either imbedded in the frond, or situated on 

 rounded sessile and stalked receptacles. 2. Pistillidia, either en- 



