352 The Botanical Gazette. [September, : 
what more complex development of the asexual phase (spor- 
ogone) in the formation of a definite multicellular wall and the 
division of the interior by a double process of cell multiplica- 
tion. Most of these details even are more orless feebly fore- 
shadowed in some of the higher alge. The only modification 
necessary in the diagrammatic representation of the lower bry- 
ophytes as contrasted with that of the higher alge is the rel- 
atively greater development of the asexual phase which is 
therefore represented by a proportionally larger loop. The 
lines of specialization which have resulted from the varied 
differentiations of this simple type will be discussed more in 
detail later in this paper. ; 
VI. The highest development of the principle of alternation 
of phases of reproduction is illustrated by the well known cli- 
max reached among the pteridophytes in which the asexual 
phase represents a degree of specialization utterly dispropot- 
tionate to the simple sexual phase (prothallus) which has 
scarcely advanced beyond the primitive condition reached by 
the lowest archegoniates. The diagrammatic repre 
of the life history of the fern is therefore a reversal of that : 
the higher alge, the larger loop representing the bi z 
ferentiated asexual phase and the smaller the simple thallose 
sexual phase. of 
The high degree of differentiation of the asexual sige 
the pteridophytes coupled with the great antiquity © e 
group have rendered them a stumbling block to pee i 
have not been careful in tracing their homologies. In the 
2 . . m 
olution of the pteridophytes, however it must be remem™™ 
“Biren comparison — 
that the line of descent must be sought, ree - = with the 
; the on 
of the highly developed asexual phase © of the simpler — 
simple sporogone of the other but along the line ne bere 
sexual phase. When we consider this feature of wees from 
opment in its proper light, the progress" of Basie 
alga to fern is greatly simplified and the distance be n of the 
groups either in the time necessary for the derivatio ntiation — 
one from the other or in the slight degree of Aim 
manifest in these coordinate phases, is reduced to 4 n is not 4 
From Higher alge to simple prothallus the pie at 
difficult one. In regard to the other feature of the Pp 
of fern-like plants which dates back to ¢ 
reached a high degree of specialization in the 
