STRUCTURE OF MARCHANTIA 



667 



themselves into the gemmae ; and these gemma?, when mature, 

 spontaneously detach themselves from their footstalks, and lie free 

 within the cavity of the conceptacle. 

 Most commonly they are at last 

 washed out by rain, and are thus 

 carried to different parts of the 

 neighbouring soil, on which they 

 grow very rapidly when well sup- 

 plied with moisture ; sometimes, 

 however, they may be found grow- 

 ing whilst still contained withfn 

 the conceptacles, forming natural 

 grafts (so to speak) upon the stock 

 from which they have been de- 

 veloped or detached ; and many of 

 the irregular lobes which the frond 

 of Marchantia puts forth seem 

 to have this origin. The very 

 curious observation was long ago 

 made by Mirbel, who carefully 

 watched the development of these 

 gemmae, that stomates are formed 

 on the side which happens to be 

 exposed to the light, and that 

 rhizoids are put forth from the 

 lower side, it being apparently a 

 matter of indifference which side of 

 the little gemma is at first turned 

 upwards, since each has the power 

 of developing either stomates or 

 rhizoids according to the influence 

 it receives. After the tendency to 

 the formation of these organs has 

 once been given, however, by the 

 sufficiently prolonged influence of 

 light upon one side and of darkness and moisture on the other, any 

 attempt to alter it is found to be vain ; for if the surfaces of the 

 young fronds be then inverted, a twisting growth soon restores them 

 to their original aspect. 



When Marchantia vegetates in damp shady situations which 

 are favourable to the nutritive processes, it does not readily produce 

 the true fructification, which is to be looked for rather in plants 

 growing in more exposed places. Each of the stalked peltate 

 (shield-like) discs contains a number of flask-shaped cavities opening 

 upon its upper surface, which are brought into view by a vertical 

 section ; and in each of these cavities is lodged an antherid which 

 is composed of a mass of ' sperm-cells,' within which are developed 

 antherozoids like those of Chara ; the whole being surmounted by a 

 long neck that projects through the mouth of the flask-shaped cavity. 

 The wheel-like receptacles (fig. 503), on the other hand, bear on their 

 under surface, at an early stage, concealed between membranes that 



FIG. 505. Gemmiparous conceptacles 

 ofMarchantiapolymorpha : A, con- 

 ceptacle fully expanded, rising from 

 the surface of the frond, a, a, and 

 containing gonidial gemmae already 

 detached. B, first appearance of 

 conceptacle on the surface of the 

 frond, showing the formation of its 

 fringe by the splitting of the epiderm. 



