GENERATIVE APPARATUS OF MARCHANTIA. 



347 



Plants) are at first evolved as single globular cells, supported 

 upon other cells vfhicli form their footstalks ; these single cells 

 gradually undergo multiplication by duplicative subdivision, until 

 they evolve themselves into the disks ; and these disks, when 

 mature, spontaneously detach themselves from their footstalks, 

 and lie free within the cavity of the conceptacle. Most com- 

 monly they are at last washed out by rain, and are thus carried 

 to difi^erent parts of the neighboring soil, on which they grow 

 very rapidly when well supplied with moisture ; sometimes, how- 

 ever, they may be found growing whilst still contained within 

 the conceptacles, forming natural grafts (so to speak) upon the 

 stock from which they have been developed and detached ; and 

 many of the irregular lobes which the frond of the Marchantia 

 puts forth, seem to have this origin. When this plant vegetates 

 in damp shady situations, which are favorable to the nutritive 

 processes, it does not readily produce the true fructification, 

 which is to be looked for rather in plants growing in more ex- 

 posed places. Each of the stalked peltate (shield-like) disks con- 

 tains 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 " antheridium," composed 

 of a mass of " sperm-cells," within which are developed " anthero- 

 zoids" like those of Chara (§ 202), surmounted by a long neck 

 that projects through the mouth of the flask-shaped cavity. The 

 wheel-like receptacles (Fig. 128) on the other hand, bear on their 

 under surface, at an early stage, concealed between membranes 

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

 " archegonia," shaped like flasks with elongated necks (Fig. 131) ; 

 each of these has in its interior a "germ-cell," to which a canal 

 leads down fi'om the extremity of the 

 neck ; and there is every reason to be- 

 lieve that, as in Ferns, the germ-cell 

 is fertilized by the penetration of the 

 antheridia through this canal, until 

 they reach it. Instead, however, of at 

 once evolving itself into a new plant 

 resembling its parent, the fertilized 

 germ-cell, or embryo-cell, developes 

 itself into a mass of cells enclosed 

 within a capsule, which is termed a 

 "sporangium;" and thus the mature 

 receptacle, in place of archegonia, 

 bears capsules or sporangia, which 

 finally burst open, and discharge their contents. These contents 

 consist of "spores," which are isolated cells, enclosed in firm 

 yellow- envelopes; and of "elaters," which are ovoidal cells, each 

 containing a double spiral fibre coiled up in its interior. This 

 fibre is so elastic, that, when the surrounding pressure is with- 

 drawn by the bursting of the sporangium, the spires extend 



Fig. 131. 



Archegonia of Marcluiniia poli/morpha, in 

 successive stages ol" developtnent. 



