650 GENERAL COMPARISON OF THE FILICALES 



either case are the same in nature and relative position, though they 



differ in their relation to the prothallus, and the foot is less fully 



developed in the Marattiaceae. 



It does not appear that the facts of the primary embryology have any 



very direct bearing on the present problem. It is interesting, however, 



to note that the axis is vertical 

 from the first in the Marattiaceae, 

 as it is also in most other Pterido- 

 phytes, and this may be held to 

 be the more primitive state for 

 Ferns : the prone position char- 

 acteristic of the Leptosporangiate 

 Ferns is exceptional among Pteri- 

 dophytes at large, and is probably 

 derivative. 



A comparative study of the 

 meristems which carry on the" 

 continued embryogeny of the Ferns 

 has brought interesting results. 1 

 Examination of the apical regions 

 of axis, leaf, and root indicates 

 that in all of these parts the 

 Marattiaceae show a relatively 

 complex state, the whole part 

 being referable in origin as a rule 

 to a group of some three or four 

 initial cells, usually of prismatic 

 form. It has also been seen in 

 them, in sections of the thick 



\ 



FIG. 352. 



A= apex of stem of Angiopteris evecta, seen from 

 above ; apparently there are four initials (x, -r). X 83. 

 7? = apex of stem of Osmunda regalis, seen from above, 

 with initial cell (x) of regular form and segmentation ; 

 /, /^leaves, the youngest (/) shows also a three-sided 

 initial cell. X 83. 



marginal wings of the leaf, that 

 at least two and possibly more 

 cells appear as initials. In the 

 typical Leptosporangiate Ferns a 

 single initial cell of conical form 

 is present at the apex of stem, 

 leaf, and root : and in the case 

 of the wings of the leaf there is a single marginal series, so that in any 

 transverse section only one initial appears. A similar examination of the 

 Osmundaceae shows that structurally they hold an intermediate position : 

 for while a single initial may be found in stem, leaf, and root, deviations 

 from this are common. In the roots of Osmunda and Todea various 



^ee Bower, Annals of Bot., iii., p. 305. Though this paper of 1889 was written 

 from the point of view then current, that the Leptosporangiate Ferns were more primitive 

 than the Eusporangiate, the facts are now equally available in their bearing on the contrary 

 view at present held. (Compare Ann. of Bot., vol. v., p. 109.) 



