OSMUND ACE. \ K 



533 



Fructifications with unmistakable Osmundaceous characters have been 

 traced back to the Jurassic period. Several species, referred by Raciborski 

 even to the genera Osmunda and Todca, have been found, bearing sporangia 

 having the characteristic distribution, form, and structure. But, as Raci- 

 borski remarks, 1 they are there so highly differentiated that their origin 

 probably dates back earlier still. I have myself pointed out that certain 

 sporangia even from the Coal period show a detailed correspondence 

 of section with those of Todea.- Without wishing to urge this similarity 

 too far, such comparisons of the propagative organs suggest an early 

 origin of the Osmundaceous stock, which is fully borne out by the existence 

 of stems, with structure, having characters both external and internal 

 comparable with those of the Osmundaceae. Such are the stems described 

 from external characters as Chelepteris by von Eichwald (Lethaea Rossica), 

 from the Permian : while these lead towards Grammatopteris, a form 

 referred to a Botryopterid affinity. These all share with the modern 

 Osmundaceae the general characters of an upright radial stock, with 

 closely disposed leaves, the bases of which persist. It will be shown 

 below that the anatomical details support the recognition of these stems 

 as a probable phyletic sequence. 



SPORE-PRODUCING MEMBERS. 



The development of the sporangium in the Osmundaceae differs from 

 that of most Ferns in the variety of its details in different individual 

 sporangia, even when they may be in 

 close juxtaposition on the pinnule. The 

 sporangia fluctuate between two types, 

 as shown by the details both in 

 Osmunda and in Todea : these are 

 illustrated by Figs. 295, which were 

 drawn from actual sporangia of Todea 

 barbara, and are not diagrams. They 



represent extreme types, the one with Young sporangia of Todea barbara in longi . 

 segmentation resulting in a square- tudinal s ." liou ' f wi different modes 



segmentation. X 365. 



based archesporium as seen in the 



Eusporangiates : the other showing the conical type characteristic of Lepto- 



sporangiate Ferns : the latter is the commoner in the Osmundaceae. 



The differences of individual detail start from the very first, as is seen 

 from Fig. 296 A, in which two sporangia are shown already projecting as 

 convex outgrowths, but the segmentation is not uniform : it is further 



FIG. 295. 



;M /ii/ir/i.. vol. xiii. , p. 7. For further data see :I!M> Se\vanl and Kurd, /.inn. 

 Trans., vol. vi., p. 250, etc. 



"Annals of Botany, vol. v., 1891, p. 109. Renault has also described as Todeof>xi^ 

 primaeva a fern sporangium from the Culm of Sanost, having Osmundaceous characters, 

 Cites Mineranx, Paris, 1896, p. 21. 



