FILICINEAE. OPHIOGLOSSEAE. 



247 



The flat apex of the stem, which is walled round by the insertions of the leaves and 

 buried in their sheaths, has a three-sided apical cell both in Ophioglossum and 

 Botrychium. The leaves have a sheathing base, and in Botrychium, as Fig. 203 

 shows, each younger leaf is completely enclosed in the one which is next above it in 

 age. In Ophioglossum the general conditions at the apex of the stem are more com- 

 plicated, because the rudimentary leaves are enclosed in a sheath of tissue, which 

 proceeds not from the base of the older leaves but from the surface of the stem, and 



B 



FIG. 202. A Ophioglossum -vulgatum. /? Rotrychium Lunaria, w roots, si stem, &s leaf-stalk, x point of branching 

 of the leaf, where the sterile lamina * separates from the fertile lamina./: Natural size. 



each leaf is thus shut in in a kind of chamber ; but an opening is left free at the top of 

 each chamber, so that the apex of the stem is in contact with the outer air through a 

 narrow canal. Both in Ophioglossum and Botrychium a root is formed normally 

 beneath each leaf. The root, like the stem, has a three-sided apical-cell *. 



As soon as the plant has reached a certain age, each leaf produces a sporangi- 

 ferous branch springing from the axile side of the leaf. In Ophioglossum both 



1 See the account of the growth of the root in the true Ferns given above. 



