668 MICROSCOPIC STRUCTURE OF HIGHER CRYPTOGAMS 



connect the origins of the lobes with one another, a set of archegones, 

 shaped like flasks with elongated necks (fig. 507) ; each of these has 

 in its interior an ' oosphere ' or ' germ-cell,' to which a canal leads 

 down from the extremity of the neck, and which is 

 fertilised by the penetration of the antherozoids 

 through this canal until they reach it. Instead, 

 however, of at once evolving itself into a new plant 

 resembling its parent, the fertilised oosphere or 

 1 embryo-cell ' develops itself into a mass of cells en- 

 closed within a capsule, which is termed a sporange ; 

 and thus the mature receptacle, in place of arche- 

 gones, bears capsules or sporanges, each of them filled 

 with an aggregation of cells that constitute the im- 

 mediate progeny of the fertilised germ-cell. These 

 cells, discharged by the bursting of the sporange, 

 are of two kinds : namely, spores, each enclosed in 

 a double spore-membrane ; and elaters, which are 

 very elongated cells, each containing a double spiral 

 fibre coiled up in its interior. This fibre is so elastic 

 that when the surrounding pressure is withdrawn 

 by the bursting of the sporange, the elaters ex- 

 tend themselves (fig. 

 506), tearing apart the 

 cell - membrane ; and 

 they do this so suddenly 

 as to jerk forth the 

 spores which may be 

 adherent to their coils, 

 and thus assist in 

 their dispersion. The 

 spores, when subjected 

 to moisture, with a 

 moderate amount of 

 light and warmth, de- 

 velop themselves into 

 little collections of cells, 

 which gradually assume the form of flattened fronds ; and thus the 

 species is very extensively multiplied, every one of the aggregate of 

 spores which is the product of a single germ-cell being capable of 

 giving origin to an independent individual. 



Marchantia is the type of the section known as the thalloid 

 Hepaticse. Another section, the foliose Hepaticse, is represented 

 by the genus Jungermannia, exceedingly common plants, of a moss- 

 like habit, growing on moist banks and similar situations. While 

 the structure of the sexual organs, and of the sporanges, resem- 

 bles in its main features that of Marchantia, the vegetative 

 organs are very different, consisting of a slender creeping stem 

 with small semi-transparent leaves. This distinct differentiation of 

 stem and leaves indicates a decided advance in organisation, and 

 marks the passage from the thallo2)hytic to the cormophytic type of 

 structure. 



FIG. 506. Elater FIG. 507. Arcliegone of Mar- 

 aud spores of c7iantiapolymorplta,msucces- 

 Marckantia. sive stages of development. 



