FILICINEM. 



413 



the central cell of the archegonium ; the first roots arise beneath it, near the base of 

 the archegonium' (/. c. p. 308). 



The processes of growth of the mature plant have not yet been ascertained with 

 as much certainty as in other Vascular Cryptogams. In Ophioglossum vulgatum and 

 Botrychium Lunaria the erect stem, buried deep in the earth and growing very 

 slowly in length, branches but rarely. Even the comparatively thick roots rarely 

 branch, and it is not known whether the branching is then monopodial or dicho- 

 tomous. [According to Holle, the roots have a 

 trilaterally pyramidal apical cell. They do not 

 branch in Ophioglossum^ and in Botrychium their 

 branches are probably produced laterally and not 

 by dichotomy.] The flattened apex of the stem, 

 surrounded by the insertions of the leaves, is buried 

 deeply in the leaf-sheaths, and shows, in Ophioglos- 

 sum vulgatum, according to Hofmeister, a three- 

 sided pyramidal apical cell as seen from above. 

 The leaves have a sheathing base, and each is 

 completely enclosed in the next older one, as shown 

 in Fig. 289 in the case of Botrychium Lunaria. In 

 Ophioglossum the relative positions of the parts at 

 the end of the stem are still more complicated, from 

 the fact that the rudimentary leaves, while com- 

 pletely enclosed one within another, produce stipular 

 structures which grow together so completely that 

 each leaf appears as if enclosed in a kind of 

 chamber formed by the cohesion of the stipular 

 parts of leaves of different ages, recalling a similar 

 arrangement in Marattia. These cohesions how- 

 ever leave an opening at the apex of each chamber ; 

 the apex of the stem is therefore exposed to the 

 air through a narrow canal (Hofmeister). 



As soon as the plant has attained a certain 

 age, each leaf bears a fructification, which forms a 

 branch springing from the axial side of the leaf. 

 In the genus Ophioglossum both the outer sterile 

 and the fertile branch of the leaf are unbranched 

 or only lobed ; in the Brasilian O. palmatum the 

 lamina is dichotomously lobed, and its margin bears 

 on each side, as it joins the petiole, numerous fertile 

 lobes or spikes of sporangia. In the genus Botry- 

 chium both are branched and in parallel planes 



(Fig. 288, A and B). The earlier hypothesis of a cohesion of the two leaf-stalks af 

 a fertile and of a sterile leaf is at once negatived by the history of development 

 (Fig. 289); the history of development rather indicates, as Hofmeister first showed, 

 that the fructification originates on the inner side of the leaf.. In the mature state 

 the fertile leaf-branch either separates from the sterile (green) one at the base or at 



FIG. 289.— Longitudinal section through the 

 lower part of a mature plant oi Botrychium I.tt- 

 naria. st stem, ^^ fibro^vascular bundles, -w a 

 young root, b apex of tlie stem, b b' b" b'" the 

 four leaves already formed, b'" the one unfolded 

 during the present year : b' shows the first indi- 

 cation of the branching of the leaf; in b" this has 

 advanced further ; tn is the median line of the 

 sterile lamina, having already its lobes right and 

 left which are not shown ;ythe fertile lamina with 

 the young branches, on which the sporangia will 

 be produced (X about lo). 



