356 The Botanical Gazette. [September, 
scarcely developed central axis to such simple modifications 
as appear in Pallavicinia and Metzgeria, in which the central 
axis becomes distinctly differentiated from the plain wing-like 
border a single cell in thickness, it is an easy step to pass to 
such pseudofoliaceous forms as Schiffneria, Fossombronia and 
Haplomitrium. From these forms again it is not difficult to 
pass to some of the simpler leafy axes like Lophocolea, Baz- 
zania, and Jungermania. It is in this group that we find the 
Hepatice attaining their greatest profusion of structure, the 
most remarkable diversity of foliar development, the widest 
range of adaptation, and the consequent abundance of genera 
and species that span the world from the lone and barren 
island of Kerguelen in the south to the inhospitable region of 
Spitzbergen in the north. Here some three thousand specits 
have been developed, and judging from the rapidity of the 
returns, it is evident that the tale is not nearly told. : 
It is, of course, impossible, within the limits of the time 
assigned, to attempt to touch upon the numerous: features of 
the evolution which this group has undergone in diverse quar 
ters of the world; we can only hint at some of the more strik- 
ing by way of illustration. . 
. The p t 1development among the Jungermaniales 
is usually slight and ephemeral; in only occasional inst A 
do we find it persistent. Perhaps the most striking yee: 
tion of this is Protocephalozia, in which the formation of 2 
occurs only as a special development for the protection : 
reproductive bodies. The antherids are borne ing by 
axils of rudimentary leaves while the perianth, subten [ pre 
slender involucral leaves, rises directly from the OTE pa 
tonema which represents the entire vegetative con ss 
the plant. a 
2. The lines of development leading from thallose ze a 
forms are numerous among the Jungermaniales, Ber is 
them have not yet been definitely correlated. Ca from 
that there is no single line of thallose genera 4s disti nui 
the foliaceous ones. While the greater part of we may 
forms do not produce their fruit terminally and ae Mets 
separated intoa distinct family which may be calle ces if 
‘ * : : eral instan 
gertacee from its typical genus, there are Sev fo with 
which thallose forms lead up toward foliaceous nial de 
which they agree in the closer relation of ater they beat . | 
opment, as well as in the more ‘important fact tha’ co 
