A nacrogynous Jungermanniales. 
J 97 
III. ANACROGYNOUS JUNGERMANNIALES. 
The Jungermanniales were divided by Leitgeb (40, 41) into a 
lower series (Anacrogynae) and a higher series (Acrogynae), for which 
Underwood (70) proposed the terms Metzgeriaceae and Junger- 
manniaceae respectively. The Acrogynas owe their name to the fact 
that the apical cell of the main axis or of a branch eventually 
becomes an archegonium, so that apical growth is arrested by the 
production of a group of archegonia. It is also characteristic of 
the Acrogynae that at least the sexual branches, and in the vast 
majority of cases the entire plant-bodies, are differentiated into 
stems and leaves, and that the young leaf divides primarily by a radial 
wall into two cells which in many cases grow out independently for 
a longer or shorter time and frequently give rise to two deeply 
separated lobes. Many of the Anacrogynas also show differentiation 
into stem and leaves, but the leaf-primordium never shows the 
initial division into two lobes ; and in all the forms placed here, 
excepting the Calobryaceae, the archegonia are borne on the upper 
side of the thallus or of the stem, the apical growth of which is 
therefore not necessarily arrested by the development of these 
organs. 
This two-fold division of the Jungermanniales is largely an 
artificial one, and as a matter of fact we find among the Anacrogynaa 
a series of types in which the development of the archegonia 
becomes, as it were, shifted nearer and nearer to the apex, while we 
have also a series of striking parallel developments, along indepen¬ 
dent lines, leading to the differentiation of a leafy shoot from a 
simple thalloid plant-body. The Jungermanniales form a single 
phylum, the boundaries between the systematic families are in most 
cases badly defined, and probably in no other group of plants do we 
find such striking and abundant examples of parallelism orhomoplasy. 
The general characters of the Jungermanniales, as contrasted 
with the Marchantiales, have already been enumerated, and we have 
seen that the two phyla are connected by the synthetic group of the 
Sphaerocarpales, which combine several of the distinctive characters 
of the Jungermanniales and Marchantiales, though on the whole 
probably standing nearer to the latter, and at the same time 
presenting peculiar features of their own. 
