STU a. LUBEOCK — PnYTOBIOLOGICAL OBSEBVATIOIS'S. 319 



cotyledons and leaves, as the name denotes, somewhat like the foot 

 of a goat ; but tlie leaves vary considerably, and it is probable that 

 the resemblance may be accidental. A clear ca^e is, however, 

 afforded by the Qnagrarlea>, where in (Enothera and some allied 

 genera the form of the mature cotyledons is evidently related to the 

 leaves, as I hope to show in a subsequent communication. Even 

 here, how^ever, tlie resemblance is confined to a basal portion of 

 the cotyledon which makes its appearance subsequent to germi- 

 nation, and no trace of it is show^u in the cotyledons themselves 

 when they first appear. 



The forms of the cotyledons in many species have been the 

 subject of special memoirs bj Tittmann, Irmisch, Wichura, 

 Winkler, Tscherning, and other botanists ; but they have not 

 given any reasons for tlie various forms assumed. 



4 



Klebs, indeed, in his interesting Memoir on Germination*, 

 refers to this diversity of form, and expressly says that these dif- 

 ferences are an enigma ('' Sind gewiss diese Verschiedenheiten in 

 den Blattformen hinsichtlich ihrer biologischen Bedeutung liir die 

 Pflanze ein Hathsel"). He observes, however, that on the whole the 

 forms of cotyledons are much simpler than those of leaves, and he 

 suggests that while in some eases, perhaps like the first leaves, they 

 retain the form which characterized the species in bygone ages, 

 w^e may rather, as a more generally applicable explanation, apply 

 to them the suggestion of Goebel with reference to stipules, and 

 regard them as simplified by arrest f ("Ihre eiufache Form einer 

 ah]. lichen liemmung verdanken, welche rielleicht fibcrwunden 

 wird, wenn es gelingt, die Kotyledonen liingere Zeit als ITaupt- 

 assiniilationsorgane bei jungen Pflanzen zu erhalten''). Even, 

 however, if this suggestion were the real explanation of the 

 comparative simplicity, it Avould throw no liglit on the differences 

 between the cotyledons of different species. 



Though cotyledons do not present nearly such extensive va- 

 riations as leaves, still they do differ considerably from bne 

 another. 



Forms of Cotyledons, 



Some are narrow^in illustration of which I may m.ention Fceni-^ 

 cuJum (fig. 5), Coreopsis (fig. G), Ceratocej)h(fhis (fig. 7), and 

 Fenda (in the hollow stalk, or ferule, of whicli Prometheus 



*'Beilriigezur Morphologic uud Eiologie Jcr Keimung," Uutersuch. BoLun. 

 Inst. V. Tubingen, 1884. 

 t Loc. cit. p. 613. 



