IV] BUDS AND BRANCHING 77 



Lyginopteris, and it has been compared with that in the Hymenophyllaceae. 

 These facts confer a special interest upon the unequal branching seen in 

 Botiyopteris cylindrica, which occurs with or without a subtending leaf 

 (Bancroft (56), Text-Figs. 7, 8). Given a high degree of inequality of the 

 shanks, and a constant subtending leaf, the condition of Zygopteris would 

 follow from the comparison of these ancient fossils. The fact that axillary 

 branching is the only regular method also for the Ophioglossaceae shows 

 the hold which it has had among primitive types, in which the biological 

 advantage may well have fixed it as a permanent feature (Hofmeister(4o), 

 p. 264; Schoute(55)). 



Fig. 71. \'ascular system of Hypolepis repens, showing the 

 departure of a leaf-trace {LT.) from the solenostele, and 

 the attachment to it of two lateral shoots, the one (l.sh.) 

 arising from the basiscopic margin of the leaf-trace, the 

 other {l.sh.') from the acroscopic margin. (After Gwynne- 

 Vaughan.) 



If on the other hand a leaf intervene between the limbs of the dichotomy 

 (as it is seen to do in Fig. 68, iv, v, vi), and if one of those limbs be arrested 

 in its development, the effect would be a bud on the abaxial face of the 

 leaf-base, attached either in the median plane, as it is seen to be in Lophosoria, 

 Metaxya, Cheiropleiiria, and others (Fig. 65): or it might be obliquely, as it 

 frequently is in creeping rhizomes, such as Deniistaedtia, Hypolepis, Marsilia, 

 or Pilularia (Fig. 72). Such differences of orientation as are suggested by 

 comparison of Fig. 68, v, vi, if slightly more accentuated, would explain the 

 difference between the conditions shown in the former and the latter groups 

 of examples. It thus becomes possible to refer both the abaxial buds and 

 those attached laterally to the leaf-base to an origin in dichotomy of the 

 axis, with unequal development of the shanks, and with a close relation of 

 a leaf to the base of the arrested shank. The vascular connections do not 

 appear to be distinctive for or against this interpretation. In Lophosoria, 



