HALLE, ON THE SPORANGIA OF SOME MESOZOIC FERNS. 13 



as compared with those of recent forms of the family but of 

 about the same size as those of the Jurassic genus Klukia 

 {civ. Seward 1910, p. 348, fig. 259). Though only the an- 

 nulus itself is distinctly preserved, there seems to be suffi- 

 cient evidence that it was apical, with radiating cells surround- 

 ing a »plate», where the wall was more delicate and has not 

 been preserved. The striation of the spores, too, as Seward 

 has pointed out, recalls a characteristic feature of the Schiz- 

 aeaceae. 



Cladotlieca Halle. 



Cladotheca undans (Lindl. & Hutt.) Halle. (PI. 2, 



figs. 9—12.) 



In a paper »On the fructifications of Jurassic fern-leaves 

 of the CladojMebis denticulata-type » the present writer de- 

 scribed, in 1911, the sporangia of the species first known as 

 Pecopteris undans Lindl. & Hutt. (1831 — 1837; vol. 2, pi. 

 120). The sporangia were found to differ markedly from the 

 structure regarded as characteristic of Todites Sew., and 

 the species was accordingly brought to a new genus, Clado- 

 theca. This type is characterized by the shortly stalked, 

 pear-shaped sporangia, which have an apical cap of thick- 

 walled cells contrasting with the thin-walled cells in the lower 

 part of the sporangium. 



Thomas' (1911, j). 385) observations on the sporangia 

 of the English Todites Williamsoni have shown that the spor- 

 angia of that specie?, or at any rate of some specimens belonging 

 to it, are not of the true osmundaceous type, as was formerly 

 supposed. The sporangia examined by Thomas are stated 

 by him to show the same general structure as those of Cla- 

 dotheca. As already noted in my paper of 1911, this discovery 

 removes the chief generic distinction between Cladotheca and 

 Todites. The difference in regard to the number and arrange- 

 ment of the sporangia was mentioned there as possibly con- 

 stituting a sufficient reason for keeping the two genera se- 

 parate. On the whole, I am inclined to think that this dif- 

 ference cannot outweigh the agreement in other respects. 

 It is possible, therefore, that Cladotheca will have to be in- 

 cluded in Todites, but there are some facts which make it 



