FERNS. ^^g 



which have their leaves arranged in many rows with a triangular apical cell, such 

 as Polytrichum\ 



The Terminal Branching of the stem which occurs in all Ferns Hofmeister con- 

 siders to be dichotomous. The branches arise very near the end of the stem, and 

 are, at least at first, like the primary stem, so that the branching is a bifurcation. 

 That the branches are independent of the leaves is inferred by this writer from the 

 fact that the ends of the stem of Pteris aquihna, which are leafless and often several 

 inches long, regularly fork. These forks are, in this and in many other cases, not 

 axillary ; and where, in other Ferns, they appear axillary, we must assume, with 

 Hofmeister, that the forking has taken place immediately in front of a youngest 

 leaf, and that the fork which stands before the leaf developes to a smaller, while 

 the other (a prolongation of the primary stem) does so to a greater extent. Thus, 

 in other words, the apparent axillary branching of some Ferns must be considered as 

 a consequence of the sympodial development of dichotomous ramifications which 

 take place in the plane of insertion of the leaves. The branching at the end of the 

 stem does not usually take place in the same plane as the insertion of the leaf imme- 

 diately preceding, and the branch then stands laterally on the stem beside the leaf. To 

 this class belongs, according to INIettenius's description, the extra-axillary branching 

 of those Hymenophyllaceae which have their leaves in two rows. That which dis- 

 tinguishes Ferns from Phanerogams with axillary branching, especially Angiosperms, 

 is the rarity of terminal branching. While in the latter every leaf-axil, at least in 

 the vegetative region, bears a bud, even the apparently axillary branches of creeping 

 Ferns with long internodcs occur mostly only at great distances, being wanting in 

 a number of intermediate leaves. In those Ferns where the growth of the stem is 

 slow and the apical region of considerable size, especially in erect species like Aspi- 

 dium Filix-7iias and Tree-ferns, the terminal branching of the stem is reduced to 

 a minimum, or is entirely absent, or occurs only in abnormal cases. 



The formation of new shoots from the bases of leaf-stalks must be distinguished 

 from the normal terminal branching of the stem. These have nothing to do 

 genetically with the stem, any more than the formation of adventitious shoots from 

 the lamina of the leaves {vide infra). 



The Development of the Leaf is decidedly basifugal and apical, the further growth 

 being also basifugal. The leaf-stalk is first formed ; at its apex the lamina begins 

 subsequently to show itself; its lowest parts are formed first, its higher parts 

 in basifugal succession. The extraordinary slowness of this growth is very re- 

 markable, finding its parallel only among the Ophioglossaceae. In old plants of 

 Pteris aquilina the formation of the leaf commences fully two years before its un- 

 folding ; at the commencement of the second year only the leaf-stalk is as yet 

 in existence, about one inch high, its growth having taken place up to this period 

 from an apical cell which is divided by oblique walls in alternating directions ; in 

 the summer of the second year the lamina arises for the first time at the apex 

 of this rod-like body, and may be found hidden in the form of a minute disc 

 beneath the long hairs. It immediately bends downwards at its apex, and hangs 



See Hofmeister, Allgemeine Morphologic, p. 509; and Bot. Zeitg. 1870, p. 441. 



