CH. XXX] 



DENNSTAEDTIINAE 



a lateral axis may be inserted close to the leaf-base. But in D. adiaiitoides 

 a local thickening appears internally at the margins of the leaf-gaps, from 

 which a projecting ridge extends into the cylinder, and is continuous from 



J'y 5.-16. A, B, C, DiaLjranis of stclar stiucture in the Dennstaedtiinae. J, Dennstaedtia 

 picncmobitia. 1 he scele including a node, and the base of a leaf-trace. The upper surface 

 of the rhizome would face the observer. It is a simple solenostele with undivided leaf-trace. 



B, a similar diagram of Dennstaedtia adiantoides : l.sh. = lateral shoot arising from the basi- 

 scopic margin of the leaf-trace l.t. i.s. = ridge upon the internal surface of the solenostele. 



C, a similar diagram of Dennstaedtia ritbiginosa: l.sh. and i.s. as in B. /, /= lacunae (or 

 perforations) in the solenostele not related to the departure of the leaf-trace. See text. 

 (AH after Gwynne-Vaughan.) 



one leaf-base to another (/?). In D. riibiginosa this ridge is represented by 

 a separate strand, which maintains its connexion with each leaf-gap, but 

 may divide into several distinct rods that traverse 

 the cylinder (Q. In a very large rhizome of D. 

 dissecta (Sw.) Moore, such rods are replaced by 

 a second complete solenostele, within the first 

 (Fig. 537). Saccolomaelegans,\\\\\c\i has an upright 

 stock with crowded leaves, goes further than this 

 in stelar elaboration. It initiates a third system 

 within the outer two, while it is also dictyostelic, 

 and the leaf-trace is already disintegrated before it 

 is detached (Fig. 538). These stelar elaborations 

 have their special interest for comparison with the essentially similar struc- 

 ture seen in the Pterideae. One further point is that perforations, not to be 

 confused with leaf-gaps, are found in D. ritbiginosa (Fig. 536, B). It will be 



Fig. 537. Transverse section of 

 rhizome o{ Dennstaedtia dissecta 

 (Sw.) Moore, showing twocom- 

 plete solenosteles. Nat. size. 



