14 Lang, Vascular Anatoinv of the OpJiioglossacece. 



they imply is unproved and is open to considerable doubt. 

 Without entering into the wide morphological questions 

 that this consideration opens up, it may be pointed out 

 that, if the explanation of the stele of HehitinthostacJiys 

 and the progression in stelar structure in the Ophio- 

 glossaceae here suggested proves to be correct, it has a 

 bearing on the theory of the origin of solenostelic and 

 dictyostelic structure in other ferns. If the structure of 

 strong rhizomes of Helunntliostacliys with a complete 

 internal endodermis has come about by elaboration of a 

 protostele without any intrusion of cortex it suggests the 

 possibility that the origin of the solenostele may also in 

 some cases have been without actual " intrusion " of tissues 

 into the xylem of the stele. If "intrusion of cortex" is 

 only a metaphor it is not inconsistent with this view ; if 

 the concept means what it signifies it requires to be 

 supported by developmental evidence. 



The facts known regarding the stelar anatomy of 

 the Ophioglossaceae appear more consistent with the 

 interpretation of the origin of a medullated stele and the 

 progression towards solenostely given by Boodle'' in dis- 

 cussing the case of the Schizaeacea^*' and stated as one of 

 the alternative methods of origin of the solenostele by 

 Gwynne-Vaughan.*' They do not support the extreme 

 view advocated by Jeffrey,'" that the pith is always due to 

 the intrusion of cortical tissues. 



The critical study of the vascular anatomy of the 

 stem and leaf-trace in the Ophioglossaceae thus suggests 



'' Annals of Botany, XV. (1901). p. 410. 



* The parallels between the Schizaeacea; and the Ophioglossacece are 

 extremely interesting. Both internal endodermis and groups of tracheides 

 appear in the medulla of Schizaea. 



» Annals of Botany, XVII. (1903), pp. ll'i, 739. 



^^ Botanical Gaze'te, Dec, 1910, p. 401. 



