512 FILICALES 
SPORE-PRODUCING MEMBERS. 
The sorus of the modern Marattiaceae is strictly circumscribed, and 
has no definite indusium: it is true that certain hairs round its periphery 
in Angiopteris have been thus described, but they hardly deserve such 
recognition (Fig. 283 B, p): also in Danaea the tissue of the leaf grows up 
between and partly envelops the sori where they are in close juxtaposition, 
and the growth has been called an indusium, but this use of the term 
is open to question (Fig. 283 kK). The sori are all constructed on a plan 
which may be described as radiate, and uniseriate, for a single series of 
sporangia are disposed in a radiate fashion round a central attachment. 
When the sorus is circular, as in Kazdfussia, the attachment is at a central 
point: when elongated, as 
in Danaea, the attach- 
ment is linear. All the 
NANO sporangia of a sorus ori- 
ginate simultaneously, a 
character which is general 
A B 
oe He G for the Simplices. The 
S sporangia themselves ma 
BNC pee ees 
cA be separate, or united into 
synangia : they are massive, 
with a broad base of in- 
Fic. 282. sertion, and each produces 
A, B, Scolecopteris elegans, Zenker, from the lower Permian. a large output of spores. 
BaNeahegierd Jolyon Bonten, nou We ceetaiae ats The dehiscence is in all 
tudinal section of a fertile pinnule enlarged (after Grand’ Eury). a 
C, D, E, Asterotheca. C=Asterotheca Miltoni, Astis, from the CASES by a slit or pore, 
Westphalian: fertile pinnules. x2. D=synangium of Asterotheca. . + sys 
pees ea eae en. be Meo Belen © 
Zeiller’s Palaebotanique.) « the distal end, or on the 
oblique inner face of each 
sporangium: there may be differences of the opening mechanism, but the 
plan of dehiscence is the same in them all. 
The structure of the mature sori of the five genera is illustrated in 
Fig. 283. Figs. a and §& represent the sori of Amgiopteris and Marattia: 
the plan of them is clearly the same, the difference being that in the 
former the sporangia are separate, in the latter they are fused -into a 
synangium, which is of firm, almost woody texture. Each sporangium in 
either case opens by a slit on the oblique inner face. The question 
will be considered later whether the synangial condition or that with 
separate sporangia is probably the more primitive: meanwhile, as regards 
the general character of the sorus, these genera may be regarded as central 
types in the family, while the rest of the genera are probably derivative. 
Thus an elongation of the sorus of Angiopteris, so that it occupies a 
considerable length of each vein, would give the condition seen in 
Archangiopteris (Fig. 283 Cc, D). It is probable that this is the correct 
