LEAF-ARCHLTECTURE AS ILLUMINATED BY A STUDY OF PTERIDOPHYTA. 691 



originally laciniate branch-system. Moreover, fig. 24, b, shows in the marginal sinus 

 which separates certain of the dichotomising vein-systems what- may be held as a 



Fig. 23. — Adult leaf of Trichomancs rcniforme, showing details of venation, and especially 

 the vascular connections before entering the petiole. + marks the limit between the 

 right and left halves of the dichotomy. Drawn by Mr J. M. Thompson. (Natural size.) 



a 



Fig. 24, a-c. — Adult leaves of Trichomancs punctatum. (x 10.) 



last relic of the merged leaf-segments. The evidence from the juvenile leaves 

 would be valuable in this relation. Unfortunately, observations on juvenile leaves in 

 this family are not extensive. But they show what would be theoretically expected, 

 if the above conclusion were true. Thus the cotjdedon of T. rigidum., Sw., as shown 

 by Goebel's drawing quoted in Natilrl. Pjianzenfam., i, 4, p. 16, fig. 11, is single- 



