674 



PROFESSOR F. O. BOWER ON 



inequality in more advanced leaves (8, 9) becomes more pronounced, while the 

 anadromic half of that which is the more strongly developed overtops the rest. In 

 (10) it has assumed the character of a terminal lobe. In this lobe in the more 

 advanced leaves a similar progression is repeated (ll), and an apparently simple 

 pinnate leaf is the result. Already in relatively small leaves the lateral pinnae may 

 repeat the same method of advance. It is perceptible in the older pinnae of (ll). 

 And thus a scheme of elaboration is initiated which has no theoretical limit. 



It corresponds to that of the other Schizseaceee, as analysed by Prantl, and it is 

 essentially the same as seen in Osmunda. All are scorpioid sympodia. In such 

 cases the chief differences lie in the earlier or later,' and the greater or less assertion 

 of the sympodial development. There is, however, one additional complication. 

 That is the formation of reticulate fusions of the veins, which appear in Lygodium, 

 § Hydrudictyon, and in Aneimia, § Aneimidictyon. This may be held to have 

 been a relatively recent acquisition. 



MarsiliacesB. 



The adult vegetative leaf of Pihdaria is simple. That of Marsilia is normally 

 four-lobed, but its juvenile leaf is simple.* The progression in M. Ernesti from the 



Fig. 8. 



-Successive stages of the juvenile leaves of Marsilia. 

 After Biiaun. 



simple to the adult was followed by A. Braun, and is discussed by GoEBEL.t 

 Braun's drawings are reproduced as fig. 8, where 1-4 show successive expansions 

 of the distal end, with dichotomous venation, the veins being linked at the margin 



* These facts compare with what is seen in Schizxa rupestris, in which, as noted by Goebel (Orgauograjihy, 

 Engl, ed., ii, p. 478), its sterile leaf is unbranched. The branching, such as is seen in the sterile leaves of 

 S. digitate and elegant, appears here only in the fertile region. 



t Very I. Entwic'kelungsges., p. 254. 



