i 95 
Phytogeny of Mar chant idles. 
rudimentary elaters like those of Boschia. But the most remarkable 
feature of Monoselenium is Goebel’s discovery that sexual receptacles 
of the “ Composite ” type may become shifted on to the dorsal side 
of the thallus, so as to occupy the same position as the arche- 
goniophores of Clevea and Plagiochasma. The writer has already 
suggested that “ the carpocephala of all the Marchantiacese, except 
Clevea and Plagiochasma, represent branch-systems.” This sug¬ 
gestion was based on the fact that several archegonia were found to 
be produced from each growing-point in the receptacles of various 
genera ( Sauteria, Peltolepis, Grimaldia, Neesiella, Rehoulia, Fim- 
briaria) in which the archegonia were formerly regarded as occurring 
singly in each involucre. Goebel’s observations on Monoselenium 
not only support this suggestion, but show that there is no need to 
exclude Clevea and Plagiochasma from the general interpretation of 
the archegoniophore as representing invariably a branch-system. 
It is clear that a “Composite” receptacle, in which the sexual 
organs are developed in centrifugal order from several growing- 
points and which is therefore a branch-system, need not necessarily 
terminate the growth of the thallus, but may come to occupy the 
sameposition as the “ dorsal outgrowth ” type of receptacle which 
Leitgeb regarded as contrasting strongly with the “branch-system” 
type. 
Goebel proceeds to elaborate the view that those members of 
the Marchantiales in which the sexual organs are borne in receptacles 
seated on the upper side of the thallus, or in which these organs 
are borne dorsally but not grouped into receptacles at all, are 
reduced and not primitive forms. He also suggests that the Riccia 
sporogonium, in which sterilisation is limited to a single peripheral 
layer of cells is not a primitive type of sporophyte, but is the lowest 
term in a descending series of forms in which the elaters become 
reduced to short sterile cells and finally are not developed at all. 
But further discussion of the wider questions raised by the study of 
the Marchantiales may be deferred until a later stage. As regards 
the systematic position of Monoselenium, it is by no means easy to 
determine the affinities of this aberrant and greatly reduced genus ; 
Goebel shows that its archegoniophore differs in several apparently 
essential respects from that of Dumortiera, while the far-reaching 
reduction of the sporogonium sets it apart from every other known 
Marchantiaceous genus. 
It is interesting to note that androgynous receptacles, in which 
antheridia and archegonia may even occur intermingled, as well as 
