362 PEACTICAL BOTANY 



remarked further that Lunularia differs from Marchantia in 

 certain structural details ; and also in the fact that, though 

 reproduction by gemmae is most profuse, a sexual reproduction is 

 not effected in this country. Thus it cannot be taken as a substi- 

 tute for Marchantia, and the material must be carefully sorted 

 before use. 



For comparison with Marchantia, observations should also be 

 made of other allied forms, e.g. Riccia fluitans, which is of 

 simpler structure, and of much smaller size ; it branches dichoto- 

 "mously, and the branches in this case often develop equally. If 

 a fresh thallus of Riccia be examined under a low power, it will 

 be seen to consist of undifferentiated green chlorophyll-containing 

 tissue, and the apex will be seen to be depressed ; on the under 

 surface will be found small amphigastria. 



As an alternative or additional type Pellia epiphylla 

 may be taken : it is a thalloid Liverwort, very commonly 

 to be found growing on moist banks, and by streams. 

 It appears as a flat expanded green thallus, with smooth 

 upper surface, sinuous margin, and slightly thickened 

 midrib. The thallus is frequently branched in a 

 dichotornous manner, but the development of the 

 branch-system is sympodial : numerous root-hairs spring 

 from the lower surface of the midrib : amphigastria are 

 absent. 



Some specimens may be found in spring to be dotted 

 over the upper surface, and especially about the midrib, 

 by numerous roundish bodies, partly sunk in the tissue 

 of the thallus these are the antheridia. Here and 

 there, on the upper surface of the same or of different 

 specimens, pocket-like cavities will be found at the 

 apex of branches of the thallus, while in spring a 

 round-headed, stalked body the sporogonium may be 

 seen projecting from each. When ripe the round head 



