CH. II MUSCINE^— HEPATIC^.— MARCHANTIACE^ 9 



gametophyte of the Muscineae is abundantly supplied with 

 chlorophyll, and therefore capable of entirely independent 

 growth. No true roots are found, but root-hairs are generally 

 present in great numbers, and these serve both to fasten the 

 plant to the substratum and also to supply it with nutriment. 



The form of the gametophyte varies much. In the 

 simplest Hepaticct, like Aneura and Pellia, it is a flat, usually 

 dichotomously branched thallus composed of nearly or quite 

 uniform cells, without traces of leaves or other special organs. 

 From this simplest type, which is quite like certain Algae, 

 differentiation seems to have proceeded in two directions ; in 

 the first instance the plant has retained its thalloid character, 

 but there has been a specialisation of the tissues, as we see 

 in the higher Marchantiaceae. In the second case the differ- 

 entiation has been an external one, the thalloid form giving 

 place to a distinct leafy axis. This latter form reaches its 

 completest expression in the higher Mosses, where it is accom- 

 panied by a high degree of specialisation of the tissues as well. 

 The growth is usually from a single apical cell, which varies 

 a good deal in form among the thalloid Hepaticae, but in the 

 foliose Hepaticae and Mosses is with few exceptions a three- 

 sided pyramid. 



The gametophyte of the Muscineae frequently is capable 

 of rapid multiplication, which may occur in several ways. 

 Where a filamentous protonema is present this branches ex- 

 tensively, and large numbers of leafy axes may be produced 

 as buds from it. Sometimes these buds are arrested in their 

 development and enter a dormant condition, and only ger- 

 minate after a period of rest. Another very common method 

 of multiplication is for the growing ends of the branches of a 

 plant to become isolated by the dying away of the tissues 

 behind them, so that each growing tip becomes the apex of a 

 new plant. Very common in the Hepaticae, but less so in the 

 Mosses, is the formation of gemmae or special reproductive 

 buds. These are produced in various ways, the simplest being 

 the separation of single cells, or small groups of cells, from the 

 margins of the leaves. In the case of Aneura mtdtifida they 

 are formed within the cells and discharged in a manner that 

 seems to be identical with that of the zoospores of many Algae. 

 Again, multicellular gemmae of peculiar form occur in several 

 of the Hepaticae, e.g. Blasia, Marchantia, where they occur in 



