LEAF-ARCHITECTURE AS ILLUMINATED BY A STUDY OF PTERIDOPHYTA. 683 



Gleich eniaceae. 

 In this relatively primitive family the leaves are profusely branched, and have 

 the well-known apical growth, interrupted as a rule by periods of inactivity. The 

 morphology of the leaf has been misunderstood in some quarters, though correctly 

 interpreted by Goebbl and others.* But a necessary step to its complete elucidation 

 would seem to be the examination of its juvenile leaves. This has been clone by 



a 



Fir,. 18, a-e. — Juvenile leaves of Glcichcnia (Dicranopieris) fulva. (a, c, d, x 5 ; 6, x 4; e, x 10 ; e\ x 30.) 



Campbell, but without fully taking up the points required.! Observations were 

 therefore made on young plants of G. (Dicranopteris) fulva, collected in Jamaica. 

 In some of the young plants the juvenile leaves develop as simple pinnate leaves 

 (fig. 18, a). In the lowest pinnae the vein may show a simple dichotomy, but in those 

 that are higher and larger the forking may be repeated with sympodial development. 

 Passing up to the apex, as the pinna diminishes the vein may be unbranched, and 

 the terminal lobe ends in a simple sympodial venation. The whole juvenile leaf is 

 constructed on a dichotomous system, as an advanced scorpioid sympodium. The 



* Organography, Engl, ed., ii, p. 318. 



t Ann. Jard. Bot. Bait., 2 s£ric, vol. viii, p. 93, ]>]s. ix, x. 



