380 



ORGANOGBAPHT. 



Fig. 812. 



free cell, called the germ or embryonal cell, is developed. After 

 fertilization, this cell enlarges and bursts through the epigone, 

 the latter either remaining only as a sort of sheath round its 

 Dase called the vaginule, or the epigone opens by a transverse 

 fissure, and the upper part is then carried upwards as a sort of 

 hood or styloid calyptra. The sporangium thus formed by 

 a development of the embryo cell, has also at times an ad- 

 ditional covering surrounding the epigone, called the perigone, 

 which frequently grows up so as to form a sort of cup-shaped 

 covering (fig. 811, b). At the base of the perigone, a number of 

 cellular filaments, perichjEtial leaves, or paraphyses, are also 

 occasionally to be found (fig. 811, c). 



The sporangia vary much in diffei'ent genera. In Marchan- 

 tia they are formed of two layers or sets of cells ; one exter- 

 nal, called the cortical or peripheral layer, and 

 one internal, in which the spores, &c., are de- 

 veloped. The cells of the cortical layer ex- 

 hibit spiral fibres, like the cells constituting 

 the inner lining of the anthers in Flowering 

 Plants. The cells forming the internal mass are 

 thus described by Henfrey : — " At an early 

 period the cells of the internal mass present the 

 appearance of a large number of filaments ra- 

 diating from the centre of the sporangium to the 

 wall. These soon become free from each other, 

 and it may then be perceived that some are of 

 very slender diameter, and others three or four 

 times as thick. The slender ones are developed 

 at once into the long elaters (fig. 812, e) cha- 

 racteristic of this genus, containing a double 

 spiral fibre, the two fibres, however, coalescing 

 into one at the ends. The thicker filaments 

 become subdivided by cross pai'titions (fig. 145, 

 a, b), and break up into squarish free cells, which 

 are the parent-cells of the spores, four of which 

 are produced in each (fig. 145, c, d)." The spo- 

 rangia in this genus are situated on the under 

 side of the receptacle, and vary in form; — they 

 burst by valves. In Jungermannia the spo- 

 rangia are elevated upon stalks arising out of 

 the vaginule ; they arc more or less oval in 

 form, and open by four valves which spread in a 

 cross-like form ; they contain spore-cells and 

 FU/-812. YAaXcTft, elUers with a single spiral filament. In An- 

 e,o{ Atarchnutia. thoceros thc SDorancfia open by two valves, and 

 have a central axis or columella ; tliey are or 

 an elongated, tubular, or conical form, situated on a short stalk, 

 and contain spore-cells and clatcrs, but tlie latter have no 



