6oo 



FILICALES 



mentioned by Prantl himself as an uncertain member of this sub-tribe. 

 An examination of its sorus shows the sporangia of various ages intermixed, 

 and without definite orientation. On these grounds the affinity of this 

 genus would appear to be elsewhere than in the Dennstaedtiinae. 



ANATOMY. 



It has long been known that the axes of Dennstaedtia and of Microlepia 

 show the structure now recognised as solenostelic ; but the detailed know- 

 ledge has lately been extended by Mr. Gwynne-Vaughan, 1 and made the 

 subject of important comparisons, of which the following paragraphs are 

 a brief abstract. The solenostele is itself held to be a relatively primitive 

 state : all the species of Dennstaedtia that have hitherto been examined 



FIG. 333 A. 



Dennstaedtia (Dicksonia) fiunctiloba. Dia- 

 gram of vascular system of rhizome, including 

 a node and the base of a leaf-trace. The upper 

 surface of the rhizome would face the observer. 

 (After Gwynne-Vaughan.) 



FIG. 333 B. 



Dennstaedtia ( Dicksonia) adiantoides. Diagram of 

 vascular system of rhizome, including a node and the 

 base of a leaf-trace, l.sh. lateral shoot arising from 

 basiscopic margin of leaf-trace: i.s. Bridge upon 

 internal surface of solenostele. The upper surface 

 of rhizome would face the observer. (After Gwynne- 

 Vaughan.) 



prove to be essentially solenostelic : similarly all the reputed species of 

 Microlepia that have been examined are also typically solenostelic, with 

 two exceptions only : one of these is Davallia (Microlepia) hirsuta, Hk., 

 which is dorsiventrally dictyostelic, and this appears structurally out of 

 place among the Microlepias : an examination of its sorus, however, shows 

 that the plant is one of the Mixtae : thus both the anatomy and the state 

 of the sorus show that its proper place is elsewhere, probably with Davallia, 

 The other exception is Davallia (Microlepia) pinnata, Cav., which appears 

 to have relations anatomically rather with Lindsaya. Excluding these it 

 may be said then that solenostelic structure is typical for Dennstaedtia 

 and Microlepia. 



The vascular relations of leaf and axis are indicated by the Figs. 333 

 A, B, c. The leaf-trace is in all cases an undivided ribbon-like strand : 

 where it is inserted upon the tubular solenostele the latter opens, forming 

 the foliar gap, which is here only short, and soon closes (Fig. 333 A). 



1 Ann. of Bot., xvii., p. 689. 



