G96 



PROFESSOR F. O. BOWER ON 



webbed condensation of a profusely dichotomous system, while the dichotomy may 

 be held to be that of the juvenile leaf retained in the adult. They resemble the 

 previous examples, but with the difference that all the veins are included in an 

 entire webbed blade. 



Fig. 28. — Basal part of the lamina of an adult sterile leaf of 

 Elaphoglossum {Rhipidopteris) peltatum. (x 4.) 



a 



Fig. 29, a-e. — A progressive series of juvenile leaves of Adiantum reniformc, 

 var. asarifolium. ( x 4.) 



A particularly good instance as bearing upon the probable secondary origin of 

 the " webbed " condition in these reniform leaves is seen in Scolopendrium Delavayi, 

 Franch., a species collected by Henry in Yunnan (fig. 30). The petiole is long and 

 the lamina reniform, with an entire margin. The venation is a sympodial dichotomy, 

 leading to a ternate structure, as indicated by brackets in the drawing ; but there is 

 no marginal involution. The distal group is a scorpioid sympoclium ; the lateral 

 ones are katadromic helicoid, after the manner of Matonia. The double sori are 



