XXl] OSMUNDACEAE 341 



It is hopeless to attempt to arrive at satisfactory conclusions 

 in regard to the applicability of the name Todites Williamsoni 

 to the numerous fronds from Jurassic and Rhaetic rocks, 

 agreeing more or less closely with Brongniart's type-specimen. 

 Specimens from the Rhaetic may not be specifically identical 

 with those from the Jurassic ; the main point is that, whether 

 actually identical or not, both sets of fossils clearly represent the 

 same general type of Osmundaceous fern^ and may for present 

 purposes be included under the same designation. The above 

 synonymy, though by no means complete^, serves to illustrate 

 the confusion which has existed in regard to this widely spread 

 type of Mesozoic fern. 



Todites Williamsoni may be briefly described as follows: — 



Frond bipinnate ; long linear pinnae (20 — 30 cm.) of uniform breadth 

 arise at an acute angle, or in the lower part of a frond, almost at right 

 angles, from . a stout rachis. Closely set pinnules attached by a broad 

 base ; slightly falcate, the side towards the rachis strongly convex and the 

 outer margin straight or concave and bulged outwards towards the base of 

 each segment, margin usually entire, or it may be slightly lobed. Fertile 

 pinnules similar to the sterile ; sporangia of the Osmundaceous type and 

 often scattered over the whole lower suface of the lamina (fig. 266, B, 

 B', G). Venation of the Gladophlehis type (cf. fig. 256, A). 



It is not always easy to distinguish Todites Williamsoni from 

 Gladophlehis cienfo'c«Zata, another common Jurassic fern, but in the 

 latter the pinnules are usually longer and relatively narrower and 

 the rachis is more slender (cf. fig. 256, B and 257). Schenk^ and 

 Raciborski* have shown that the sporangia of Todites conform 

 in the absence of a true annulus to those of Todea (fig. 256, G) 

 and Osmunda. Nathorst® has recently figured a group of spores 

 of Todites Williamsoni in illustration of the use of the treat- 

 ment of carbonised impressions with nitric acid and potassium 

 chlorate. This species, though widely distributed in Jurassic 

 rocks, is hardly distinguishable from the German Rhaetic fronds 

 figured by Schenk from Bayreuth as Acrostichites Goeppertianus^, 



1 Seward and Ford (03) p. 251. 



2 For a more complete list, see Seward (00) p. 87. 



3 Schenk (85) PL iii. fig. 3. ■* Eaciborski (94) A. PL vi. 

 s Nathorst (08) PL i. fig. 7. « Schenk (67) A. 



