440 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



late receptacles, to the under side of which the sporangia are 

 attached, accompanied by various involucres. They occur in 

 all parts of the world, but, perhaps, are more numerous in 

 warmer climates. The species, moreover, have a wide geo- 

 graphical range. Marcliantia polymorpha, for instance, 

 occurs in all temperate climates, and appears in Java and 

 Abyssinia. Its power of enduring heat, provided there be 

 plenty of moisture, is shown by its flourishing as it does in 

 hothouses. Every genus occurs in Europe, with the exception 

 of the doubtful Rhacotheca, which at present has been 

 found only in the Azores. The species appear to be of little 

 use. Medicinal properties are attributed to some, and the 

 different species are popular remedies in England for jaundice, 

 consumption, and other maladies ; but their virtues are, in all 

 probability, quite imaginary ; and within my own experience 

 Marchantice are vulgarly confounded with Peltigerce. 



484. The genera are distinguished by the manner or extent 

 to which the receptacle is lobed, by the greater or less crowd- 

 ing of the sporangia, by the nature of the involucre, and, above 

 all, by the way in which the sporangium bursts. In Fegatella 

 the receptacle is reduced to the thickened apex of the pedun- 

 cle ; in some cases, as in Duvalia, it is quite entire ; in 

 Marchantia (Fig. 91, a) it bursts by means of short teeth ; 

 in Preissia, by several deep lacinias ; in Scmteria and Dumor- 

 tieria (Fig. 92, a), it is semivalvate ; in Fegatella, the teeth 

 are re volute ; in Rehoulia the sporangium is irregularly torn 

 or sub-operculate ; in Grimaldia it is horizontally divided in 

 the centre (circumscissum) ; in Duvalia and Fimhriaria, 

 above the centre, so as to form a sort of operculum ; in Rha- 

 cotheca, the mode of rupture is variable, being semivalvate or 

 horizontal. 



485. The archegonium or calyptra does not always embrace 

 the sporangium closely, as in Riccia, but looks like a proper 

 involucre. The proper involucre or perianth is sometimes regu- 



arly fissured, as in Fimbriaria (Fig. 92, b), for the escape of 

 the spores. The peduncle of the female fruit, it should be 

 observed, is not similar all round. One side is generally 

 strongly grooved, while the other is round. It has, in fact, an 



