MARSILIACEAE 551 
It is then specially through Zygodium that the nearest connection may 
be sought with ancestral Fern-types, which should have a protostelic stock, 
and show dichotomy both in axis and in leaf: large sporangia, with the 
annulus not necessarily uniseriate, and with a relatively large spore-output. 
As these characters are less decisive than those seen in the preceding 
families, the difficulty in locating the Schizaeaceae will be correspondingly 
greater. 
MARSILIACEAE. 
It is probably in near relation to the Schizaeaceae that the Marsiliaceae 
find their most natural position. This has been argued: by Campbell,! and 
the data relating to the sporangia appear specially convincing. But as these 
heterosporous plants constitute a peculiarly specialised line, which has 
probably never advanced further, the discussion of them, however interesting 
in itself, does not bear directly upon the problem in hand. Accordingly no 
detailed .account will be given of the Marsiliaceae. 
There is, however, one striking feature in their morphology which calls 
for notice here, since it provides an apparent analogy with the Ophio- 
glossaceae: viz. the position of the “sporocarp.” This curious and complex 
body may be stalked or sessile and be borne singly attached to the leaf- 
stalk, or in considerable numbers as in JZ. polycarpa: finally it may itself 
be branched. From its position and structure, as well as from the way in 
which the sporangia are produced, a foliar character is probable, notwith- 
standing that the form is far removed from that of any ordinary leaf-segment : 
and this is the conclusion to which study of the development has clearly led. 
Johnson? found that both in Marstlia and Filwlaria the origin of the 
sporocarp is from a cell of the marginal series of the leaf: he concludes 
that the capsule is the equivalent of a branch of a leaf in which the 
marginal cells have been devoted to the formation of sporangia instead of 
alamina. Goebel obtained a somewhat similar result from the investigation 
of 7. polycarpa :* here the numerous sporocarps arise in acropetal succession 
from the margin of the leaf, but from one margin only: they assume upon 
the leaf-primordium the same position as the sterile pinnae. But the arrange- 
ment of the cells is different: the sporophylls have a two-sided initial, while 
the sterile pinnae show from the first a marginal growth. This, however, 
need not preclude the recognition of the sporocarps as the correlatives of 
pinnae. 
The analogy of these bodies with the spikes of the Ophioglossaceae is 
too obvious to escape remark, and some have seen in them and their 
pinna-character strong evidence that the same must be the nature of the 
Ophioglossaceous spike. The objections to this facile conclusion are two: 
1 American Naturalist, 1904, pp. 761-775. 
2 Ann. of Bot., xii., p. 119; and Bot. Gaz., xxvi., p. f. 
3 Organography, vol. ii., Pp. 479. 
