LEAF-ARCHITECTURE AS ILLUMINATED BY A STUDY OF PTERIDOPHYTA 681 



B. virginianum, though more profusely branched, while the higher lobation of the 

 latter is indicated in the segments of the former only by sinuosities of the margin. 

 But B. ternatum is not an extreme case. Fig. 16 shows the apical region of a 

 leaf of B. Jenmani, Und, where the branchings in each lobe are more numerous, 

 while the webbing is so complete that only a slight sinuosity of the margin is seen. 

 Its condition approaches that well known in B. Lunaria, in which, though laciniate 

 forms have been described,* the outline of the lobes in normal forms is virtually 

 smooth. This is shown in fig. 17, in the case of one of the youngest plants observed. 



Fig. 14. — Apex of adult leaf of Botrychiuin 

 virginianum. ( x 2. ) 



Fig. 15. — Apical lobe of an adult leaf of 

 Botrychiuin ternatum. (x 4.) 



The venation is like that of B. Jenmani, and it may be compared with that in 

 Osmunda regalis, while the laciniate state of B. virginianum resembles Todea 

 superba. It has been suggested that the Osmunda type is the result of " webbing" 

 of a laciniate type such as T. superba, and the same would apply to the forms of 

 Botrychium. The co-existence of webbed and laciniate forms of the same genus or 

 species, or even on the same plant, is a common feature in Ferns. It is seen very 

 prominently in the species of Schizsea ; S. dichotoma having narrow segments and 

 S. elegans being webbed in varying degree, but with similar branching of the veins. 

 Comparison may also be made of Asplenium dimorphum, quoted by GoEBEL.t 



The cotyledons of B. ternatum and Jenmani have not been seen. But Mr 

 Harold Lyon sent me some years ago a photograph of young plants of B. (Scep- 



* Rab. krypt. Flora, iii, p. 558, fig. 176. f Organography, Engl, ed., ii, p. 478, fig. 316. 



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