XXI] 



ANATOMY 



137 



are two possible views of such facts: eitlier that the state we see is the result 

 of reduction from a more complex vascular condition; or that the system 

 itself is in the up-grade of a relatively primitive evolution, in fact that the 

 living examples illustrate approximately the limit of such development as 

 their direct ancestors ever attained. The former opinion has been elaborated 

 by Jeffrey {PJiil. Trans, cxcv, p. 119, etc.) and by Faull {Bot. Gaz. 1901, 

 p. 381). They hold the Osmundaceous stele to be a reduced form of "amphi- 

 phloic siphonostele," and in support of their opinion they adduce the 

 presence of an internal endodermis in O. cimiamomea and T. hymenophylloides, 

 and the occasional presence of internal phloem also locally in the neighbour- 

 A B 



"1 



Fig. 428. A, scheme showing part of the xyiem-niig of Osmtinda regalis 

 as it would be seen from without ; /./. =cut end of a departing leaf-trace; 

 Lg. = xylic-gap. (After Lachmann, from Kidston and Gwynne-Vaughan.) 

 /)', a similar scheme for Todea Barbara^ seen from without. Lettering as 

 above. (After Seward and Ford, from Kidston and Gwynne-Vaughan.) 



hood of the branchings of the axis. There are good grounds for doubting 

 whether the local and inconstant occurrence of endodermis and internal 

 phloem will bear the weight of a far-reaching theory of reduction. It 

 would appear less likely that a robust and large-leaved phylum of Ferns 

 should show a reduced vascular system in its stock than that the stock 

 should retain a primitive though perhaps imperfectly efficient system. 



The contrary opinion, viz., that the stele of Osmunda is in the up-grade 

 of development, though showing a relatively primitive structure, was enter- 

 tained by Zenetti, who made a careful study of its anatomy {Bot. Zeit. 

 1895, pp. y2-y6). A good basis for an opinion opposed to a theory of 

 reduction is found in the ontogeny of the living species: for in their sporelings 



