528 FILICALES 
The late definition of the parts of the embryo is in accord with the 
indefiniteness of the apical segmentation of these Ferns. There are some 
though inconstant signs of a single initial cell in the apex of root and stem of 
the embryo; but the apices of the mature parts of the Marattiaceae, whether 
axis, leaf, or root, show as a rule a more complex structure, three or 
more commonly four initial cells being recognised. This arrangement of 
the meristems is in accord also with the Eusporangiate character of these 
Ferns. Many years ago! I showed that a parallelism exists in the Filicales 
between their sporangial origin and the meristems of all the vegetative parts; 
that in the Leptosporangiate Ferns, where the whole sporangium originates 
from a single parent cell, the apical meristems of stem, leaf, and root are 
referable also to the segmentation of a single initial cell; but that in the 
Eusporangiate Marattiaceae the apical meristems are more complex, with 
no single initial With this goes also the deeply sunk character of the 
sexual organs on the prothallus. Thus the general conclusion must be 
that in all its parts the Marattiaceous type differs from the Leptosporangiate 
type in its greater robustness of construction. 
The account given in the preceding pages includes facts which show 
good reason for holding to the early existence of plants, of a Maratti- 
aceous type. Not only does this follow from the detailed comparison of 
Pecopterid-sori with those of the living Marattiaceae, but also from the 
structure of the Psavonius-stems. From evidence of comparative structure 
and association it appears certain that the Psarvonzus-stems bore the foliage 
of Pecopterts of the same nature as the leaves on which various synangic 
fructifications have been found. Thus we have to do with a group of 
Palaeozoic fossil-plants showing affinity with the Marattiaceae alike in their 
anatomical structure and in their reproductive organs. But certain fructi- 
fications previously clagsed as Marattiaceous have lately been shown to be 
the pollen-apparatus of Spermophytes, e.g. Crossotheca and Pecopteris (Dick- 
sonites) Pluckenett. Considering the anatomical evidence, however, it seems 
impossible to doubt that Palaeozoic Marattiaceae actually existed, for the 
Psaronius-type of stem is altogether Fern-like in structure, and presents 
none of those anatomical features by which the Cycadofilices were recog- 
nised long before the evidence of fructification led to the foundation of 
the class Pteridospermeae. For the present, therefore, we must continue 
to accept the existence of a certain number of Marattiaceous Ferns, 
especially in the later Carboniferous and Permian periods, though we may 
not always be able to distinguish their fructifications from the pollen- 
bearing organs of Fern-like Seed-Plants. It seems not improbable that 
Marattiaceae and Pteridospermeae may have owed their synangic fructi- 
fications to some common descent from a primitive group of Filicales in 
which that character had already appeared.? 
1 Ann. of Bot., 1889, vol. iii., p. 305. 
2 This paragraph is taken almost verbally from Scott, ‘‘ Present position of Palaeozoic 
Botany,” Progressus Rei Botanicae, 1907, pp. 187-189. 
