VII PTERIDOPHYTA—FILICINE^—OPHIOGLOSSACEM 261 



giophore not yet differentiated. At the base of the youngest 

 leaf is the stem apex. The whole bud is covered in this species 

 with numerous short hairs, which are also found in B. ternatuin 

 and some other species ; but in B. simplex and the other simpler 

 species it is perfectly smooth, as in Ophioglossum. The young 

 leaves in B. Virginianum are bent over, and the segments of the 

 leaf are bent inward in a way that recalls the vernation of the 

 true Ferns. The sporangiophore grows out from the inner 

 surface of the lamina, and its branches are directed in the 

 opposite direction from those of the sterile part of the leaf. 



Fig. 142. — Boirychium Virginianum, A, Rhizome and terminal bud of a strong plant, 

 the roots and all but the base of the oldest leaf removed, X i ; B, longitudinal sec- 

 tion of the bud, X3; st, the stem apex; I. II. III., the leaves; C, transverse sec- 

 tion of the petiole, X4; D, transverse section of the rhizome, X about 16; P, 

 the pith; m, medullary rays; x, xylem; c, cambium; phj phloem; sh, endodermis. 



The vascular bundles of the stem are much more prominent 

 than in Ophioglossum, and form a hollow cylinder, with small 

 gaps only, corresponding to the leaves. This cylinder shows 

 the tissues arranged in a manner that more nearly resembles the 

 structure of the stem in Gymnosperms or normal Dicotyledons 

 than anything else. Surrounding the central pith (Fig. 142, P) 

 is a ring of woody tissue (.r) with radiating medullary rays 

 (w), and outside of this a ring of phloem, separated from the 



