62 • BOTANICAL GAZETTE [tanttary 



ing character of the stipules— being large, stout, and thorny; slender, 

 terete, rigid, and sharp-pointed; long, weak, and membranaceous; 

 small or evanescent or flattened and glandular-capitate, etc —in 

 the different groups; they occur in situations much resembling the 

 situations occupied by the stipules. All of these facts suggest that 

 the compounding of the leaf with organization of partial leaf-stalks, 

 in evolution, has been the occasion for the production of stipels 

 homoeotically. 



Moreover, we may well suspect that in many cases decompounding 

 of the blade has followed upon compounding from the same general 

 cause; the partial blades borrowing the compounding tendency from 

 the parent blade, the whole leaf thus becoming by a single step 

 decompound. The circumstance that the ground-plan of the whole 

 leaf is repeated in miniature in the several parts, in a vast number 

 of decompound leaves of both phanerogams and ferns, and the 

 occurrence of the corresponding type of homoeosis as individual 

 variation in both divisions, lend a color of probability to this con- 

 ception. Decompounding, on this hypothesis, would have no initial 

 relation to utility, and would not be a product of natural selection. 



To consider this matter a little further with respect to ferns : If 

 the variation which we find so frequently in ferns has been the basis 

 of evolutionary advance in complexity of the frond, we should be 

 able to discover in the decompound-leaved species certain relations 

 which would necessarily follow from such an evolution. We should 

 certainly find the ground-plan repeated in the segments. We should 

 expect to find, further, that the historically earlier and simpler condi- 

 tions would be retained in youthful leaves; and that these youth- 

 ful leaves would be matched by the segments of the fully developed 

 fronds of the mature plant. Both these expectations are met in many 

 species. Ferns on every hand illustrate the first. Of the second, a 

 single example will be enough to direct attention to the facts which are 

 easily observable. In fig. i 9 are reproduced a youthful frond of 

 rolysttchum angulare proliferum, and a pinna from an adult leaf. 

 in Asplemum Filix-foemina we have a depauperate variety, var. 

 exile D. C. Eaton, the mature frond of which is very precisely 



44 See Eaton's Ferns of North America pi. 7 6. 



form 



