MOSSES AND FERNS 



CHAP. 



next divided by a vertical wall, perpendicular to the broad 

 faces of the segment, into two cells, in which divisions then 

 take place in both transverse and longitudinal direction without 

 strict regularity. 



The stem is mostly made up of thin-walled parenchyma, 

 and the vascular bundles are much less developed than is the 

 case in the underground stem of O. vulgatum or Botrychium. 

 The bundles are of the collateral form, i.e. the inner side is 

 occupied by the xylem, the outer by the phloem, and there 



Fig. 115. — Ophioglossum pendiibiin (X:). A, Longitudinal section of stem apex, x6o; B, the central 

 part of the same section, X 180 ; D, longitudinal section of very young sporangiophore, X 180 ; E, 

 cross-section of young sporangiophore, X 60. 



is no bundle -sheath developed. The bundles form a very 

 irregular wide-meshed cylinder, not differing essentially from 

 that in 0. vulgatum. 



The young leaf is completely concealed by the sheath 

 formed by the base of the next older one. It is at first a 

 conical protuberance arising close to the stem apex, around 

 which its base gradually grows and forms the sheath about it 

 and the next leaf rudiment. It is probable that here, as in 

 0. vulgatum} the young leaf grows at first by a definite apical 



^ Rostowzew (i). p. 451. 



