II MUSCINE^— HEPATIC^— MARCHANTIALES 47 



antheridial receptacles are sometimes stalked, but more com- 

 monly are sessile, and often differ but little from those of the 

 higher Ricciaceae. 



The sporogonium shows an advance upon that of the 

 Ricciaceae by the development of a lower sterile portion, or foot, 

 in addition to the spore-bearing portion or capsule, and in the 

 latter there are always sterile cells, which in all but the lowest 

 Corsinieae have the form of elaters. At maturity, also, the ripe 

 capsule breaks through the calyptra, except in the Corsinieae, 

 where, too, the sterile cells do not develop into elaters, but 

 seem to serve simply as nourishing cells for the growing 

 spores. The stalk of the capsule is usually short compared 

 with that of most Jungermanniaceae, and the wall of the capsule 

 remains intact until the spores are ripe. 



The spores vary much in size, and in the development of 

 the outer wall. In Marchantia polymorpha and other species 

 where the spores germinate promptly, the ripe spore contains 

 chlorophyll, and the exospore is thin and slightly developed. 

 In such cases there is no distinct rupture of the exospore, but 

 the whole spore elongates directly into the germ-tube. In 

 Conocephalus, where the spores are very large, the first divi- 

 sions occur in the spores before they are scattered. In species 

 where the spores do not germinate at once the process is much 

 like that of Riccia, and the thick exospore is ruptured and 

 remains attached to the base of the germ-tube. 



The apical growth of the Marchantieae is very much like 

 that of Riccia. In Fimbriaria Californica (Fig. 14) the apical 

 cells seen in vertical section show the same form as those of 

 Riccia, and the succession of dorsal and ventral segments is 

 the same; but here the development of the ventral segments 

 is much greater, and there is not the formation of the median 

 ventral lamellae as in Riccia, but the two rows of ventral scales 

 arise independently on either side of the midrib, very near the 

 growing point, and closely overlap and completely protect the 

 apex. The formation of the lacunae in the dorsal part of the 

 thallus begins earlier than in Riccia, and corresponds very 

 closely to what obtains in Ricciocarpus. The pits are at first 

 very narrow, but widen rapidly as they recede from the apex. 

 In the epidermal cells surrounding the opening of the cavity, 

 there are rapid divisions, so that the opening remains small 

 and forms the simple pore found in this species. As in Riccio- 



