520 FILICALES 
as a slight modification of this, by localisation of the sclerotic thickening 
so as to form a hoop-like band, while the remaining walls are thin. 
It is thus seen that the sporangia of the living Marattiaceae conform 
essentially to a single type: but that that type is less definite in its 
detailed characters than is the case in other Ferns: and this goes along 
with their larger size, and the 
high output of spores, which is 
its natural concomitant. For 
on computation in round num- 
bers, the sum of the spores 
potentially present in a_ spor- 
angium of Angiopleri’s is about 
1450: of Danaea about 1750: 
of Marattia about 2500: and 
of Kaul/fussia about 7850. It 
is thus seen that the synangial 
forms have the largest number. 
This, with various other con- 
siderations, will have weight 
in the discussion whether the 
state with synangia or that with 
separate sporangia is probably 
the more primitive. 
Passing now to the fossil 
Ferns having _ fructifications 
which may be ascribed to a 
Marattiaceous affinity, many of 
them had foliage of the Pecop- 
terid-type (Fig. 287), though this 
in itself cannot be held as any 
Pai-o88 clear indication of relationship : 
ee ee a eee eae See it is the soral structure which is 
pinnule (lower surface), showing numerous synangia. B, distinctive. A few of the best 
synangia in side view. (4 and & x about 6.) (After Grand’ 3 
EKury.) C, asynangium in section parallel to the surface of known examples will be de- 
the leaf, showing severt eonflucne sporangia. a, bundle of 
receptacle ; 4, its parenchyma; c, tapetum ; @, spores; e,, scribed, with a view to their 
common envelope of icity « about 60. (After i - : 
Renault.) From Scott’s Studies in Fossil Botany. comparison with the fructifica- 
tions of the living Marattiaceae. 
One of the most striking is Ptvchocarpus (Pecopterts) unita:’ here, on the 
lower surface of the pinnules of a Pecopterid leaf, the sori are disposed 
on either side of the midrib: each is a solid synangium, composed of 
about seven sporangia united upon a common receptacle. Each synangium 
is attached by a short and narrow pedicel, so that it may be removed 
bodily, and the synangia are frequently found lying free. The form is 
that of a truncated cone, with a slight terminal dimple. The sporangia 
TRenault, Bass’n Hourller da Autun, ii., p. 9. 
