78 



ANALYSIS OF THE SHOOT-SYSTEM OF FERNS [CH. 



Metaxya, and Cheiropleiwia the supply to the bud appears to arise from the 

 base of the leaf-trace: in Dennstaedtia and Hypolepis, where the bud is lateral, 

 the relation is with the margin of the leaf-trace. The question here is whether 

 the leaf bears the bud, or the bud on its departure immediately gave rise to 

 the leaf Gwynne-Vaughan on anatomical grounds held the former view, 

 but the latter seems the more probable interpretation on grounds of com- 

 parison. That the reference of the buds to an origin by dichotomy is correct 

 as applied to Marsilia and Pilularia is indicated by reference to the related 

 genus Schizaea, in which there is equal dichotomy. 



Fig. 72. Pilularia globiilifera. {a) Rhizome with alternate leaves, and a bud associated with each 

 of them; note circinate vernation (after Velenovsky). {b) Apical bud, with hairs removed, seen 

 from above. 3 — 7 the successive leaves; b^ — /;, the successive buds, one at the base of each leaf; 

 rg— rg, the corresponding roots, (c) The extreme up-turned tip of a similar apex seen from above; 

 I' I" the youngest alternate leaves ; b„ the bud corresponding to /". (d) Section vertically through 

 a corresponding leaf and bud, showing the apical cell of each ; h, /z = hairs, [(a) about natural size ; 

 [b) X70; (0 X175; {d) X325.] 



While it may thus be possible to interpret the buds about the leaf-base 

 in Ferns in terms of distal branching unequally developed, there are cases 

 which are obviously not of that nature. The buds borne on the upper regions 

 of the leaf, whether substitutionary for soral development or not, are locally 

 distinct in their origin from the axis. This and their late appearance mark 

 them as adventitious. But there are other buds which present difficulty in 

 interpretation. As examples of these the buds on the persistent leaf-bases 

 oi Dryopteris Filix-nias may be quoted (Fig. i, B, C). Their position at some 

 distance from the leaf-insertion and their relatively late appearance have 



