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 u, D): 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 K). 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 Kaulfussia, the attachment is at a central 



point : when elongated, as 

 in Danaea, the attach- 

 ment is linear. All the 

 sporangia of a sorus ori- 

 ginate simultaneously, a 

 character which is general 

 for the Simplices, The 

 sporangia themselves may 

 be separate, or united into 

 synangia : they are massive, 

 with a broad base of in- 

 sertion, and each produces 



FIG. 282. 



B, Scolecopteris elegans, Zenker, from the low*- Permian. a large Output of 



A= transverse section of a fertile pinnule enlarged (after Zenker). 

 morpha, Brongn, from the Stephanian, longi- 

 fertile pinnule enlarged (after Grand' Eury). 



B^Scolecopteri 

 tudinal section 



The dehlSCCttCe IS in all 



. 



C, D, E, Asterotheca. C = Asterotheca Miltoni, Astis, from the CaSCS by a Silt Or pore, 



Westphalian : fertile pinnules. X2. Z? = synangium of Asterotheca. . ,. 



X about 6. = longitudinal section of a pinnule of A sterotheca, in a median position at 



traversing three synangia, enlarged. (After Grand' Eury, from ,, j- . i j -u 



7jt\Vitx'& Paiaebotanique.) the distal end, or on the 



oblique inner face^ of eacl 



sporangium : there may be differences of the opening mechanism, but th< 

 plan of dehiscence is the same in them all. 



The structure of the mature sori of the five genera is illustrated ii 

 Fig. 283. Figs. A and E represent the sori of Angiopteris and Marattia 

 the plan of them is clearly the same, the difference being that in tl 

 former the sporangia are separate, in the latter they are fused into 

 synangium, which is of firm, almost woody texture. Each sporangium ii 

 either case opens by a slit on the oblique inner face. The questioi 

 will be considered later whether the synangial condition or that witl 

 separate sporangia is probably the more primitive : meanwhile, as regards 

 the general character of the sorus, these genera may be regarded as centi 

 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 

 considerable length of each vein, would give the condition seen ii 

 Archangiopteris (Fig. 283 c, D). It is probable that this is the correct 



