Acrogynous Jungermanniales. 295 
who reproduces the general phylogenetic scheme suggested by 
Schiffner for the Acrogynae. It is only fair to add that neither of 
these writers discusses the question in detail, and that both put 
their views forward in a tentative fashion. A careful comparison 
of the structure and development of the gametophyte and sporo- 
gonium in the Lejeuneaceae and the Aneuraceae shows that there 
are two points of apparent resemblance between these groups. 
Taking first the sporogonial characters, which led Schiffner to 
suggest the possible origin of Lejeuneaceae from Aneuraceae, we find 
the resemblances are purely superficial. It is true that in both 
series elaters remain attached by their upper ends to the four valves 
of the dehisced capsule-wall, and that there is consequently a 
general similarity in the mechanism by which the spores are 
scattered. There are, however, fundamental differences in the 
structure and development of the capsule in the two families. In 
the Aneuraceae, we find a solid mass of sterile tissue, forming an 
incomplete apical columella or elaterophore and splitting at dehis¬ 
cence into four portions which remain fixed to the capsule-valves; 
some of the elaters are attached to this elaterophore, the rest being 
free and mingled with the spores. In Lejeuneaceae, on the other 
hand, there is a regular alternation between (1) elaters fixed apically 
and extending the entire depth of the capsule-cavity, and (2) longi¬ 
tudinal rows of spores ; there is no elaterophore, and all the elaters 
are fixed. The occurence of elaters fixed by their upper ends to 
the inside of the capsule-wall in various genera of Acrogynae widely 
removed from the Lejeuneaceae in the current system of classification 
forms an additional argument, if any be necessary, against the 
existence of any close connexion between the Aneuraceae and the 
Lejeuneaceae as regards the structure of the sporogonium. The 
Lejeuneaceous capsule is, in fact, much more readily derived from 
that of, say, Cephalozia or Lepidozia, than from that of Aneura or 
Melzgeria. In Cephalozia, Lepidozia, and several other genera, 
most, if not all, of the elaters are fixed by one end to the capsule- 
wall and radiate towards the centre and the base of the capsule- 
cavity (Pig. 50, IV.), and from this type the arrangement character¬ 
istic of the Lejeuneaceae can easily be derived. The resemblances 
between the Aneuraceous and Lejeuneaceous types of capsule- 
structure appear, in short, to be entirely illusory. 
Much more striking is the resemblance between the Aneuraceae 
and Lejeuneaceae in the early stages of development of the gameto¬ 
phyte. Except for the absence of a midrib, the thalloid vegetative 
