6i4 MOSSES AND FERNS 



Targioniaceae. The characteristic lobing of the spore mother cells, 

 found in the Jungermanniales, is conspicuous in Monoclea, but occurs 

 also in Targionia, though not so markedly. The long seta of the 

 sporophyte can be explained by the semi-aquatic habit of Monoclea 

 (see Cavers (9) ). 



P. 71. Goebel (27) has recently described a very remarkable 

 Marchantiaceous type, Monoselenium, which shows some striking 

 indications of reduction, comparable to those in Monoclea and Dumor- 

 tiera. Like these, there is a complete disappearance of the air-chamber, 

 but evidences of reduction are also shown in the reproductive parts. 

 The sexual organs are similar to those of the higher Marchantiaceae, 

 and are borne on special receptacles of the same type ; but the sporo- 

 phyte is much simpler, approaching in structure that of Corsinia or 

 Boschia. The sterile cells may show the character of true elaters, 

 or they may be undifferentiated nutritive cells like those of Sphcero- 

 carpus. 



P. 71. Cavers (6) thinks that Leitgeb's division of the Marchan- 

 tiaceae into the three groups, Astroporae, Operculatae and Compositae, 

 is to some extent a natural one. The sporogonium wall in the first 

 and third groups shows (usually) fibrous thickenings of the cell-wall, 

 these thickenings being absent in the Operculatae. The apical cap, 

 or lid, found in the Operculatae, does not, however, seem to be essen- 

 tially different from the similar apical cap which is formed in many 

 of the Compositae, e.g, Wiesnerella, Marchantia. 



CHAPTER III 



P. 73. Recent investigations have shown that the differences 

 between the antheridia of the Marchantiales and Jungermanniales 

 are less marked than has been assumed. Thus in Fossombronia 

 (Humphrey (i)), the early divisions in the antheridium resemble 

 those of the Marchantiales, and in Pellia (Hutchinson (i) ) this is 

 also sometimes the case, although usually the divisions follow those 

 of the typical Jungermanniales. 



P. 75. The classification of the Jungermanniales is still far from 

 satisfactory. Cavers (9) has proposed to remove the "Anelatereae" 

 from their association with the other Anacrogynae, and to establish a 

 distinct order, Sphaerocarpales, intermediate between the Junger- 

 manniales and the Marchantiales ; and there is a good deal to be said 

 for this suggestion. 



