538 



FILICALES 



from a more complex condition, or that the system is itself in the upgrade, 

 and an indication, as seen in the living examples, of the approximate 

 limit which development had attained in the group. The former opinion 

 has been elaborated by Jeffrey l and by Faull : - they hold the Osmundaceous 

 stele to be a reduced form of " amphiphloic siphonostele," and in support 

 of their opinion they adduce the presence of an internal endodermis 

 (O. cinnamomea and T. hymenophylloides), and the occasional presence in 

 some specimens of O. cinnamomea of internal phloem also, locally in the 



* / I I 



I J I _ 



FIG. 299. 



/i=a representation of a portion of the xylem-ring of Osmunda rcgalis seen from 

 without; /^ = cut end of a departing leaf-trace; 4s> = leaf-gap. (After Lachmann, from 

 Kidston and Gwynne-Vaughan.) j5 = a representation of a portion of the xylem-ring of 

 Todea barbara, seen from without. Lettering as above. (After Seward and Ford, from 

 Kidston and Gwynne-Vaughan.) 



neighbourhood of the branchings of the axis. There are good grounds 

 for doubting whether the local and inconstant occurrence of internal phloem 

 and endodermis will bear the weight of a far-reaching theory of reduction : 

 the question has been argued sufficiently elsewhere, 3 on grounds of anatomical 

 comparison of living forms, and without acceptance of the reduction theory. 

 Kven on grounds of physiological probability 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. 



Apart, however, from such questions of probability, a good basis for 



'/'////. Train,, vol. cxcv., p. 119, etc. 



-"Anatomy of the Osmundaceae," Bot. Gaz., 1901, p. 381. 



3 Scott, A r :"iv Pliytologist, vol. i., p. 209; Seward, I.e., p. 255; Boodle, Ann. of 

 Bot., 1903, p. 518; Chandler, Ann. of Bot., 1905, p. 406. 



