ORGANS OF EEPRODrCTIOX. 



371 



arranged in different genera ; thus in Biccia they are imbedded 

 in the substance of the frond, while in Jungerynannia and Mar- 

 chantia {fig. 813) they are contained in receptacles, r, which are 

 elevated above the thallus on stalks, .«?. They are usually small 

 flask-shaped bodies, consisting of a cellular case or epigone {fig. 

 814), having a canal in its upper elongated portion which leads 



Fig. 813. 



Fig. 813. A portion of 

 the thallus of Marchan- 

 tia polyviorpha. r. Re- 

 ceptacle supported on a 

 stalk, s. Ou the under 

 surface of the recep- 

 tacle the archegonlaare 



imbedded. Fig. 814. 



Archegonium of 2Iar- 

 chantia. b. Peri gone, 

 open at its apex, and 

 surrounding an inner 

 cellular case or epigone, 

 c. Paraphyses. 



Fig. 814. 



to a cavity, at the bottom of which a single free cell, called the 

 germ or embryonal cell, is developed. This germ-cell is doubt- 

 less fertilized, as in Ferns and Mosses, by the passage of the 

 antherozoids down the canal until they come in contact with it. 

 The fully developed archegonia, like those of Mosses, have also 

 at times an additional covering surrounding the epigone, called 

 the perigo7ie, which frequently grows up so as to form a sort of 

 cup-shaped covering {fig. 814, b). At the base of the perigone, a 

 number of cellular filaments, pericheetial leaves, or paraphyses, 

 are also occasionally to be found {fig. 814, c). 



As in the case of Mosses, the fertilized germ-cell does not 

 directly develop a new plant like its parent, but after fertiliza- 

 tion the germ-cell enlarges and bursts through the epigone, and 

 forms a sporangiiim or capside ; the epigone either remaining 

 as a sort of sheath round the base of the sporangium, which is 

 called the vaginide, or its upper part is carried upwards as a 

 sort of hood or styloid cah/ptra. 



The sporangia vary much in different genera. In Marchantia 

 they are formed of two layers or sets of cells ; one external, 

 called the cortical or peripheral layer, and one internal, in 

 which -the spor<='S,&c., are developed. The cells of the cortical 

 layer exhibit spiral fibres, like the cells constituting the inner 

 lining of the anthers in Flowering Plants. The cells forming the 



