THE FERNS 533 
certain ferns closely related to the above more nearly resembles 
that of Anthoceros, and is holophytic, as we may suppose to have 
been the case with the original fern-ancestor. When we compare 
the sporophytes of an adder-tongue and a horned liverwort, how- 
ever, so many striking differences appear, that it may at first seem 
hopeless to think of homologizing the parts. Indeed, we have in 
ferns true leaves, stems, and roots, no trace of which appear in any 
liverwort. But we have sporangia in both, and in the growing zone 
of Anthoceros we have a cylindrical meristematic organ suggesting 
possibilities of much further differentiation. If the sporangium of 
Ss. 
sy % 
yy 5d a 
we, yy 6 
Fic. 358.—Grape-fern. A, gametophyte (prothallus) cut vertically to 
show the antheridia (an), the archegonia (ac), and the pseudo-roots (w), 
5°. B, lower part of a young sporophyte dug up in September, cut 
vertically to show the stem (st) and leaves (5, b’, b’’), 22. (Hofmeister.) 
Fic. 359.—Adder-tongue. Upper part of spore-bearing division of leaf (§), 
cut vertically to show the tip (s), the spore-cavities (sp), the places (r) 
where a slit is formed to free the spores, and the woody strands or fibro- 
vascular bundles (g) which strengthen and conduct sap. (Sachs.) 
Anthoceros were enlarged and instead of elaters produced sterile 
tissue between groups of spores forming two rows on either side of 
the columella, the resulting organ would be a flat spike of sporangia 
like that of Ophioglossum (Fig. 359). What may have happened 
is that in very ancient times, before the age when coal plants flour- 
ished, a liverwort something like an Anthoceros did evolve a root 
from the lower end of its growing zone, which made possible an 
expansion of the green tissue above, while this in turn helped to 
bring about the formation of two rows of globular sporangia making 
a flat cluster as already described. Such an expanded member 
