246 PHYLUM VIII. BRYOPHYTA 



On germination the spores produce gametophytes like 

 the originals. 



430. The very conspicuous Great Liverwort (Mar- 

 chantia) is common on moist ground and is frequently 

 abundant in green houses. Its gametophyte is a large, 

 flat, branching, thalloid plant with a distinct midrib. 

 Its epidermis is pierced with circular, many-celled 



"stomata" which open into large 

 air cavities supplied with many 

 green cells. Here and there on the 

 upper surface are cups containing 

 hairs whose terminal cells develop 



into g 1 " 6611 maSS6S ( br d ^aSSCS, Of 



gemmae) which fall off and quickly 

 develop into new gametophytes. This is thus an asex- 

 ual mode of reproduction, and these brood masses take 

 the place of the zoospores, tetraspores, 

 and conidia of lower plants. 



431. The antherids are confined to par- 

 ticular portions of the gametophyte (an- 

 theridial disks) which are raised on short 

 stalks. Here they are sunken in the sur- 

 face and they and the sperms resemble 

 those of Riccia and Anthoceros. 



432. The archegones are also confined to particular 

 portions of the gametophyte (known as "receptacles" 



but really lobed disks) which are raised 

 on more or less elongated stalks (arche- 

 gonial branches). The archegones are 

 dependent from the under side of the re- 

 ceptacle. When fertilized the egg de- 

 " ve ^P s mto a globose, shortly stalked 

 sporophyte containing spores and elon- 

 gated sterile cells, the "elaters," whose walls are spirally 



