58 



OPHIOGLOSSACEAE 



[CH. 



ir '^^ 



In B. Lnnaria a protostele with solid xylem is found at the base of the 

 young plant. Passing upwards it be- 

 comes medullated, the change being 

 intra-stelar, apparently resulting from 

 an absence of thickening in the in- 

 nermost procambial cells : but not 

 uncommonly isolated tracheides lie 

 embedded in the pith thus explaining 

 its origin (Fig. 349). The further steps 

 seen in BotrycJiiwn, resulting in foliar 

 gaps with a partial internal endo- 

 dermis, have already been described 

 in Vol. I, p. 131, while Lang's recon- 

 structions of the stele make clear the 

 amplifications from the original proto- 

 stele which appear in the adult shoot 

 (Fig. 350), Other species of Botry- 

 chiumy even the largest of them, 

 possess the same essential structure. 

 But in addition a secondary cambial 

 activity may arise, traces of which 

 are already seen in B. Lunaria (Fig. 

 350, i5). But in B. virginianum this 

 may be effective in producing a con- 

 siderable mass of secondary wood, 

 traversed by medullary rays (see 

 Vol, I, Fig. 129, p. 137). Where a 

 leaf-trace is given off a sector of the 

 xylem-ring becomes detached, and 

 passes outwards, thus opening the 

 xylic ring : but throughout the de- 

 parture of the leaf-trace in the young 

 plant, the stele and the trace are both 



Fig. 350. Botrychium Lunaria. ^ = reconstruc- 

 tion of the stelar structure by Lang, of his 

 plant E. i? = a similar reconstruction of his 

 plant F, only the xylem and endodermis are 

 indicated, the former black ; the latter as a 

 line where seen in section, but dotted where 

 the endodermis is seen in surface view, as if the 

 stele were split in half. The leaves are really 

 arranged spirally, but they are here repre- 

 sented as though they arose alternately. The 

 level of origin of the root-traces is indicated. 

 The proportions have been altered from those 

 in nature so that the stele is represented as 

 broader in proportion to its length than is 

 actually thecase: ( x ) represents axillary buds; 

 (*) the apex. (After Lang.) 



enclosed by endodermis, and it is only 

 in the adult that the foliar gap opens giving direct connection between the 

 cortex and the pith. Similarly with the root-traces, which are given off 

 irregularly in position and number, as will be seen from Lang's recon- 

 structions. 



The massive creeping rhizome of Helminthostachys, bearing its leaves less 

 crowded and only on its upper side, gives a better chance of elucidation of 

 its stelar structure than do the short upright stocks of Botryclwun, and it 

 has been fully examined by Farmer and by Lang. In the juvenile stem 



