6o 



OPHIOGLOSSACEAE 



[CH. 



Fig. 352. Origin of the leaf-trace oi Helminthostachys, after Lang: a, before 

 the endodermis opens; /;, the separation of the leaf-trace; <r, the leaf-trace 



rounded off, and "Ciepsydroid' 

 the origin of root-traces. 



in form ; the stele not yet closed shows 



the trace departs with endarch structure, the inner xylem having disappeared 



from the trace-sector. Thus the inner xylem is more strictly cauline than 



the outer. In Botrychium, however, the inner xylem seems to have been 



wholly replaced by pith. Such facts are 



out of harmony with a phytonic theory 



such as that advanced by Campbell. The 



stelar structure of HeluiintJiostacJiys is in 



effect a rudimentary type of solenostele, 



with foliar gaps which do not as a rule 



overlap (Fig. 353). 



The stelar state of OpJiioglossum is 

 variable, as might have been expected 

 from the diversity of its species. In some 

 the base of the plant is protostelic with 

 solid xylem, which becomes medullated 

 upwards as in the other genera (Bower, 

 Ann. of Bot. xxv, PI. xxv. Fig. 2). But 

 in others it may be medullated from the 

 first: and this is seen particularly at the 

 base of the root-buds of O. palmatiwi. 

 At the lower part of the plant an outer 

 endodermis may be found in the smaller 

 species {0. Bergianuin, cape use, ellipticum 



Poirault): but in most species it is absent. Passing upwards the medullated 

 stele expands into a reticulum with leaf-gaps, well shown in Rostowzew's 

 dissections (Fig. 341, 4, 5). The meshes are large and the leaves arranged 

 in a compact spiral : as a rule a root-trace passes off below each leaf-insertion. 

 The leaf-trace in O. vulgatum, and in Eu-Ophioglossuin generally, is undivided 

 as in the other genera. Transverse sections of the stock accordingly show 

 an interrupted ring of vascular strands consisting chiefly of xylem, and with- 



Fig. 353. Helviinthostachys zeylanica 

 Hook. The upper figure represents the 

 vascular skeleton, dissected out. Z.= 

 leaf-trace ; R. = root-strand ; F.g. = foliar 

 gap. The lower figure shows the rhi- 

 zome-stele giving off a leaf-trace L. T., 

 which breaks up above into separate 

 petiolar strands. 7?. = root-trace. (After 

 Farmer and Freeman.) 



