On the Gaps in the Stele of 

 some Polypodiaceae. 



By 



Yudziirii Oii'ura. 



Since tlie end of the last century, the problem of the stele has 

 been discussed by many authors, especially with regard to Pteridophy- 

 tes, and various nomenclatures about the stele were introduced. Among 

 them Solenostele and Dictyostele may be adopted here, as was done 

 by Tansley^\ for the stele with single tubular form. 



Solenostele was defined by Gwynne-Vaughan-^ as "a single hollow 

 cylinder with phloem and phloeoterma on either side, the complete 

 continuity of which is interrupted only by the departure of leaf-traces ; 

 the gap thus produced being closed up in the internode above before 

 the departure of the next leaf-traces." Dictyostele was defined by 

 Brebner''^ in the following manner : "a vascular tube with large 

 overlapping leaf-gaps, so that the whole structure becomes a network 

 of vascular strands or meristeles. The meristeles are concentric. 

 This is closely allied to the preceding (Solenostele), the difference 

 being due to the approximation and overlapping of the leaf-gaps." 



The distinction between these two stelar forms depends on the 

 presence or absence of overlapping leaf-gaps, but there are other 

 types of steles, in which gaps other than leaf-gaps are present. They 

 were called by Tansley^^ as 'perforated' and 'dissected' steles. If 



1} Tansley, a. G. (1907-S) Lecture on the evolution of the filicmean vascular 

 system. — New phyt, Vol. 6-7. 



2) Gwynne-Vaughan, D. T. (1901 &03) Observations on the anatomy of soleno- 

 telic ferns. -Ann. Bot., Vol. 15 & 17, '01, p. 73. 



3) Brebneb, G. (1902) On the anatomy of Danaea and other Marattiaceae. 

 —Ann. Bot, Vol. 16, p. 523. 



4) Tansley, 1. c. '07, p. 192. 



