APPENDIX 6ii 



R. glauca, while Garber and Lewis give but four chromosomes in the 

 spores of R. natans. 



The primary division walls separating the young spores, according 

 to Beer, are a pectose-cellulose compound, while the secondary thicken- 

 ing of the walls shows the presence of callose. 



The spore coat is composed of three parts, an outer coat which very 

 early shows cutinization ; a middle coat, also more or less cutinized, 

 and itself showing a differentiation into three laminae ; and finally the 

 inner coat, or endospore, which arises late in the development of the 

 spore, and which shows pectose and cellulose reactions. 



Beer thinks that the materials necessary for the development of 

 the spore membranes is derived mainly from the disintegration of the 

 outer sterile cells of the sporophyte, and the inner cells of the calyptra, 

 but that there is probably a certain amount of nutritive matter 

 transferred from the vegetative tissues of the gametophyte. 



P. 39. The more recent studies of Ricciocarpus (see Cavers (9) ) 

 indicate that this genus should be united with Riccia, as was originally 

 done. 



P. 40. Tesselina has recently been discovered in the Southern 

 United States (Howe (6) ). 



P. 41. Corsinia marchantioides occurs in the south of Europe and 

 in the Canary Islands and Madeira. Stephani (i) states that it has 

 also been reported from Louisiana. Boschia Weddellii is known only 

 from Brazil. 



P. 42. Barnes and Land (2) have made an extended study of the 

 origin of the air-chambers in the Marchantiales, and conclude that 

 in all cases these begin by the formation of an intercellular space just 

 beneath the epidermis, and that the superficial pores, or stomata, 

 are formed secondarily by the subsequent extending of the inter- 

 cellular space to the surface. From Deutsch's study of Targionia, 

 however (Deutsch (i) ), as well as from the writer's studies on Fim- 

 briaria, it appears that sometimes, at any rate, as in Riccia, the first 

 evidence of the air-chamber is a pit between the epidermal cells, 

 which later extends to the underlying tissue. 



There are two well-marked types of air-chambers. In Fimhriaria 

 Calif ornica, for example (see Fig. 14), through the rapid enlargement 

 of the thallus, the air-chambers become very large and irregular in 

 form, and there is not a sharp distinction between this lacunar tissue 

 of the dorsal region and the solid tissue of the ventral region. 



In the second type, which is seen in Targionia and Marchantia, as 

 well as in most other Marchantiaceae, the lacunar tissue consists of a 



