G10 
MR. F. O. BOWER ON THE COMPARATIVE MORPHOLOGY OF THE 
podium) is to be distinguished from the upper part of the leaf (epipodium) ;* and 
again in Gnetum Gnemon, where the winged epipodium may be distinguished from the 
mesopodium or petiole, and this is slightly different in conformation from the swollen 
basal portion or hypopodium. Such distinctions are only to be drawn where they are 
warranted by the exigencies of description : Eichleb, asserted that the distinction of 
“ blattgrund ” and “ oberblatt ” is common to the leaves of all Phanerogams ; t such a 
general application is as unnatural and prejudicial as was the general application of 
the spiral theory of leaf-arrangement. 
Finally, there remain those more complicated forms of leaf which are not included 
in the series of large-leaved Vascular Cryptogams and Gymnosperms above described. 
The well-known development of the leaf in Marsilia corresponds in many respects to 
that of the typical leaf in the Ferns ; it may be regarded as a reduced type 
connecting them with the still further reduced members of the Hydropteridece. 
The leaf consists of a phyllopodium bearing four pinnae, of which the lower pair 
are formed by monopodial branching, while the upper pair are described as being 
the result of bifurcation of the apex of the leaf. In Botrychium Lunaria, in which 
the details of arrangement of the meristem, and other points in the development of 
the foliage-leaf are but imperfectly known, there is a well-marked phyllopodium, 
preserving imperfectly the characters of a winged structure. It bears pinnae in two 
longitudinal rows ; the order of their development is stated by Holle (Bot. Zeit., 
1875, p. 274) to be acropetal, and this coincides with my own limited observations. 
In the mode of development, external conformation, and arrangement of the pinnae 
it is not unlike Zamia. The apex of the leaf frequently terminates in an equal pair 
of pinnae, which recalls the similar arrangement in Marsilia, and further the leaf of 
Ginkgo ; but frequently there is a somewhat flattened terminal process, which 
projects beyond the last pinnae ; such forms constitute an instructive series con¬ 
necting a decidedly monopodial branching with cases of apparent dichotomy. In 
Ophioglossum the phyllopodium is not branched, its apical part developing as a 
flattened expansion. In Helminthostachys it is branched, but details of the develop¬ 
ment of the leaf have not yet been published. 
The foregoing pages will have amply shown that the more complicated forms of leaf 
among the Vascular Cryptogams naturally lend themselves, throughout their whole 
length, to a consistent morphological treatment as branch-systems ; while in those 
* Tlie leaf of Isoetes stows intermediate characters between those of Angiopteris and of the Cycadacece. 
There is no apical cell, and apical growth is not strongly defined; pericliual divisions of superficial cells 
are frequent throughout the leaf, from apex to base, but especially on the ventral side ; intercalary growth 
is strongest at first below the ligule, and then diminishes in that part, and extends to the upper part of the 
leaf. These characters as well as others suggest that Isoetes may be a form intermediate between the 
Marattiacece and Cycadacece, in which the vegetative organs have been reduced in structure and external 
form in accordance with its aqueous habit. 
t l.c., p. 7 : “ Zwei Haupt-theile, die alien phanerogamischen Blattern gemeinsam sind.” 
