938 XI. HEPATIC^. 



small cell whicli 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 of lunule. 



Sepatie<s 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 (JRiellid). Other Hepaticee 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 branchlet. 



The leaves of the caulescent Hepatiece 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 Sehginella. 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 amphigastria (or stipules). When the leaves are alternate the spiral arrangement is from right 

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

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

 dage which forms a sort of wing {Oottschea), or they have a small basal raised fold (Jjejeunid), 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 Jungermanniea are so arranged that the lines of insertion of two consecutive leaves 

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

 membranous expaiLsion spread upon the earth. 



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

 of the group of Jungertiimmiecs. 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 Finibriaria. The perianth remains nearly entire and 

 campanulate in Lejewnia ; it is cylindric in many true Junyermanniece ; it is absent in some genera, and 

 replaced by leaves in Oymnomitrium. With the exception of Marchantia, Fimhriaria 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 Hepaticm the perigonium [inflorescence] contains but one archegonium {Marchantia, &c.). 

 In Jungermanniece it always contains several, all but one of which are abortive ; in Sarcoscgphus two or 

 three are developed. The name perichcetium or perichietial leaves is given to the outer envelope or involucre 

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

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

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



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

 hronia). In this little plant the antheridia are free, shortly pediceUed, 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 Marchantieee the antheridia occupy 

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

 {Marchantia poly morpha), or are sessile on the margin of the fronds {Fegatella conioa), or they form small 



