356 



MOSSES AND FERNS 



CHAP. 



The roots arise regularly, two at the base of each leaf/ 

 and their bundles connect with those of the stem near the 

 bottom of the elongated foliar gap in its vascular cylinder. 



The Sporaitgia 



The sporangia in Osniunda are produced upon sporophylls 



that closely resemble those 

 of Botrydiiuin or Helinmtlio- 

 stachys, but in Todea they occur 

 upon the backs of the leaves, 

 as in most Ferns. In structure 

 and development they are 

 intermediate between the true 

 leptosporangiate type and the 

 eusporangiate. So far as they 

 have been investigated they all 

 correspond very closely. The 

 origin of the sporangia is al- 

 most identical with that in 

 Botrydiiuin, and more than 

 one cell may take part in their 

 formation.^ Bower says : " In 

 all cases, however, one cell 

 distinctly takes the lead, and 

 this we may call the initial 

 cell (Fig. 183, A); but the 

 arrangement of its division 

 walls does not, as in the true 

 leptosporangiate Ferns, con- 

 form to any strict plan ; the 

 Fig. 184.— A, Apical view ; B, front view of ripe initial cclls are oblong, scen in 



sporanaium of O. cinnamoviea ; r, annulus, . , . :i l.\- C. t- 



r,. ^ vertical section, and the hrst 



X43. 



divisions are longitudinal, so 

 as to meet the basal wall : both in the segment thus cut off and 

 in the central cell, periclinal or sometimes oblique divisions may 

 take place, so that a considerable bulk of tissue is formed, in 

 the projecting apex of which a single large cell occupies a 

 central position." Like Botrychium the archesporium is derived 

 from a single hypodermal cell, which approaches more or less 



^ Lachmann (7), p. 118. 



2 Bovver (11), p. 362 ; Goebel (17), p. 387. 



