938 XL HEPATIC^. 



small cell which serves as a pedicel. In Lunularia, which covers the damp earth 

 of our gardens, this cup resembles an arched vase, or a semicircular basket, whence 

 its name oflunule. 



Hepaticts are very naturally grouped, according to their vegetative organs. Some present flat 

 dichotomous membranous fronds appressed to the soil by means of rootlets, and usually nerveless, but 

 furnished with stomata ; more rarely the membranous frond twists spirally around a sort of axis formed 

 by the nerve (Riellia). Other Hepaticte have a simple or branched prostrate or erect stem, and are fur- 

 nished with true leaves. The stem sometimes creeps over the soil, emitting fronds at different distances, 

 and then simulates a rhizome or runner (JlageUa). The ramification is usually dichotomous, as in 

 Lycopods and Ferns; but one of the branches is sometimes arrested, or changed into a secondary flagelli- 

 form branch let. 



The leaves of the caulescent Hepaticee are extremely varied in form, but are nevertheless so charac- 

 teristic in each genus as to enable botanists to describe the species without seeing the reproductive 

 organs. These little leaves, without nerves or stomata, are opposite or alternate, and their insertion 

 resembles that of Sclaginclla. Usually they are nearer the upper than the lower surface of the stem, and 

 in the intervals are seen, turned towards the soil, a third series of smaller leaves, obliquely inserted, 

 named atnphiyastria (or stipules). When the leaves are alternate the spiral arrangement is from right 

 to left (Fntllania), or from left to right (Lophocolea). The leaves and amphigastria are always sessile ; 

 but the leaves are not always Hat and spreading ; they have often on their upper surface a crest or appen- 

 dage which forms a sort of wing (Gottschca), or they have a small basal raised fold (Ly'eunia), or a sort 

 of pouch open at both ends (Frullania). These modifications, though apparently very slight, affect all 

 the species of the genus, and the form of these pouches is constant in the same species. 



The leaves of Juiigermanniea are so arranged that the lines of insertion of two consecutive leaves 

 converge, and represent an erect or reversed V. In Anthoceros the vegetative system consists of a simple 

 membranous expansion spread upon the earth. 



The form and position of the perianth have supplied a methodical division of the caulescent Hepaticee 

 of the group of Junyermanniere. This perianth, which is identical in structure with the leaves, forms a 

 cup or small urn, sometimes contracted at the top, which in this case is ruptured to allow the passage of 

 the sporangium. But this dehiscence presents many modifications: it results in four nearly equal 

 segments in Marchantia ; in numerous strips in Fimbriaria. The perianth remains nearly entire and 

 cnmpanulate in Lejeunia ; it is cylindric in many true Junyermannieee ; it is absent in some genera, and 

 replaced by leaves in Gymnomitrium. With the exception of Marchantia, Fimbriaria and Preissia, it is 

 absent in the tribe of Marchantieee. The pedicel which bears the sporangium is always cylindric, cellular, 

 very delicate, usually transparent and colourless ; its growth is often very rapid. 



In most Hepaticte the perigonium [inflorescence] contains but one archegonitim (Marchantia, &c.). 

 In Junyermannieee it always contains several, all but one of which are abortive ; in Sarcoscyphn* two or 

 three are developed. The name pericfuetium or pericheetial leaves is given to the outer envelope or involucre 

 of the perianth. The perichaetium originally envelops the archegonium with its styliform appendage ; 

 the perigonium is formed afterwards. In Calypogeia, Harpanthus, &c., there is only a perigonium and no 

 perichsetium ; while in Gymnomitrium, Schisma, &c., there is a perichaetium and no perigonium. 



The antheridia of Hepaticee were first observed by Schmidel on Jungermannia pusitta, L. (Fossom- 

 bronia). In this little plant the antheridia are free, shortly pedicelled, and planted on the central 

 nerve of the frond. The cells of its walls contain bright yellow granules, which cause the antheridium 

 to resemble a grain of pollen. When the antheridia are fully developed, the top cells become markedly 

 turgid; this indicates the moment of dehiscence. Thuret, from whom we have taken most of these 

 details, has observed the following phenomena : the cells which form the upper half of the antheridium 

 suddenly bend in the opposite direction to that previously occupied ; a complete discoloration is the 

 result, and the contents of the antheridium are set free, when a membrane or cuticle covering or connect- 

 ing the cells becomes visible. The antherozoids are flexible, furnished with two hairs, and the arche- 

 gonia are in juxtaposition with the antheridia. In the tribe of Marchantiece the antheridia occupy 

 peculiar receptacles of very varied form ; sometimes they are little pedicelled disks with waved edges 

 (Marchantia polymorpha), or are sessile on the margin of the fronds (Fcgatella conica), or they form small 



