218 



BOTANY 



young leaf, which would ordinarily develop into its lower lobe, intersecting walls 

 arise which cut out a tetrahedral cell, at once transforming it into the apical cell 

 for the new shoot. 



Reproduction 



Gemmae. Unicellular or bicellular gemmae are found in many forms, and 

 usually arise from marginal cells of the leaves, falling off readily and germinating 



much as the spores 

 do. Less commonly, 

 e.g. Lejeunia metz- 

 geriopsis, multicel- 

 lular gemmae are 

 produced. 



Sex-organs. 

 The plants may be 

 either monoecious or 

 dioecious. In the lat- 

 ter case, as in the 

 common genus Ma- 

 dotheca (Bellin- 

 cinia), (Fig. 175), 

 the reproductive 

 branches are some- 

 what different from 

 the sterile ones. The 

 antheridia (Fig. 177) 

 are borne singly in 

 the axils of closely 

 imbricated leaves, 

 upon short lateral 

 branches. Theanthe- 

 ridium corresponds 

 in its development 

 with that of the Ana- 

 crogynae, but is often 

 long-stalked, and in 

 Madotheca has the 

 lower part of the wall 

 more massive than 

 is usually the case. 



Archegonium. 

 The archegonia are 

 borne upon short 

 lateral branches also, 

 and arise from segments of the apical cell (176, D), which finally becomes trans- 

 formed into an archegonium. This arrests the further growth of the shoot. The 

 group of archegonia is usually surrounded by an inflated involucre, similar to 

 that found in many other Liverworts. 



FIG. 179. Madotheca Bolanderi. A, nearly median longi- 

 tudinal section of an advanced embryo (X 260). , upper 

 part of the same (x 525). C, sporogenous cells and 

 young elaters from an older sporophyte (X 525). 



The Sporophyte 



The development of the sporophyte in the Acrogynse is very much like that 

 of the lower Jungermanniales. Here, also, the whole of the sporophyte, except 



