242 



MOSSES AND FERNS 



CHAP. 



trial species of Ophioglossuni, the development of the leaves is 

 very slow. 



In most species of Botrychium the relation of the leaf base 

 to the young bud and stem apex is the same as in OpJiioglossuin, 

 except that the sheath is more obviously formed from the leaf 

 base ; but in B. Vh'ginianuni the sheath is open on one side, 

 and more resembles a pair of stipules. Fig. 123, A shows the 

 stem and terminal bud of a plant of this species with all but 



B. 



Fig. 123. — Botrychium Virginianuni (Sw.)- 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 section of the bud, X 3 ; st, the 

 stem apex ; I. II. III., the leaves ; C, transverse section of the petiole, X4 ; D, transverse section 

 of the rhizome, X about 16 ; P, the pith ; in, medullary rays ; x, xylem ; c, cambium ; pk, 

 phloem ; sh, endoderniis. 



the base of the leaf of the present year cut away, and B the 

 same with the bud cut open longitudinally. At this stage the 

 parts of the leaf for the next year are well advanced, and the 

 formation of the individual sporangia just begun. The leaf for 

 the second year already shows the sporangiophore clearly 

 evident, and the leaf which is to unfold in three years is 

 evident, but the sporangiophore 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 



