404 Dr. G. Ogilvie on the Forms and Structure of Fern-stems. 



the petioles allows them greater prominence. This form of stem 

 would probably be better termed a right or straight than a 

 simple caudex, for it generally bears lateral buds, giving rise to 

 secondary rhizomes (PI. X. fig. 10). Sometimes these appear to 

 be deciduous, or to be pushed off by the growth of the petioles. 

 In any case, they will of course become independent plants when 

 the decay of the lower extremity of the caudex reaches their 

 points of origin. 



As examples of this form of caudex may be mentioned, Lastrea 

 Filix mas, L. dilatata, L. cristata, Polystichum aculeatum, and 

 P. Lonchitis. 



The other form of caudex is intermediate between this last 

 variety and the stoloniferous rhizome first described; for the 

 axis branches so repeatedly in a dichotomous manner, by the 

 duplication of its terminal buds, that, when dissected out, it has 

 somewhat the character of the stoloniferous rhizome ; but in its 

 natural state it is so thickly set both with foot-stalks and root- 

 lets, that nothing is to be distinguished but a mass of tangled 

 roots, more or less tufted above and densely fibrous below. 



A caudex of one kind or other occurs in all our larger Ferns 

 except Pteris aquilina, and in the majority it appears to be 

 branched. So at least it is in Allosurus aispus, Blechnum bo- 

 reale, Osmunda regalis, Lastrea Oreopteris, and in Filix foemina 

 and the genus Asplenium generally. (PI. VIII. fig. 3; IX. figs. 4, 

 5, 6.) 



It is doubtful if the branched caudex ever becomes arbores- 

 cent as a normal occurrence*. Branched Tree-ferns are cer- 

 tainly met with, but rather, it would seem, as an occasional 

 abnormality than as a regular form. 



Among our native Ferns, Ophioglossum and Botrychium are 

 remarkable for their vernation being straight, not circinate, as 

 in the rest of the group, and the last-mentioned species also 

 for the edges of the solitary petiole cohering, so as to embrace 

 the point of the axis and form a cavity which lodges the embryo 

 of the next year's frond ; within its petiole the rudiments of the 

 frond of the succeeding year may in like manner be detected. 

 The stem itself may probably be considered a modification of 

 the simple caudex. 



Among the Fern-allies of our flora, the stoloniferous is the 

 most common form of stem. In Equisetacese it is subterranean, 

 like that of the Ferns; but in Pilularia and Lycopodium it 

 creeps along the surface of the ground. In the larger species 



* An analogical argument in favour of this may be drawn from Palm- 

 stems, which are normally simple from the development of a single terminal 

 bud, but which are branched in a few species, as Phoenix, or form lateral 

 buds, as in Areca, Caryota, and Chamarops. 



