
20 THE AMERICAN NATURALIST. (VoL. XXXIX. 
evidently related to the leaves. Even here, however, the resem- 
blance is confined to a basal portion of the cotyledon which 
makes its appearance subsequent to germination, and no trace 
of it is shown in the cotyledons themselves when they first 
appear." 
We can readily see from Lubbock's work that a morphological 
leaf-value has been ascribed to cotyledons solely on their resem- 
blance to foliage leaves, a resemblance which is acquired after 
germination when the cotyledons are functioning as photosyn- 
thetic areas. Then they are only in general leaf-like, for if any 
cotyledons be compared with the foliage leaves of the same 
plant they are found to differ from these, usually to a marked 
degree in form, texture and venation. The resemblance is never 
more than such as might be wholly induced by the assumption 
of the vegetative function, for the cotyledons become function- 
ally similar structures in the same environment as the leaves. 
Natural forces seem to call forth a remarkably constant type of 
foliar organ in all those plants where any extent of tissue is 
specialized for this purpose no matter what the morphological 
value of the tissue may be. The gametophytes of some mosses 
develop leaves which are quite similar to the simpler leaves 
produced by the sporophytes of many pteridophytes and phan- 
erogams. Phyllodes and Phylloclades are well known cases 
where the assumption of the function has, in many instances, 
been followed by the assumption of the form of leaves. 
Ramaley has undertaken a study of the comparative anat- 
omy of cotyledons and leaves. In his paper (:03) on the coty- 
ledons and leaves of the Papilionacez, he writes: “In the 
plants. examined, all of which have cotyledons which function 
for a tme as leaves, the anatomical structure is strikingly differ- 
ent in cotyledons and leaves... The stalk of the cotyledon 
when present has a structure different from that of the leaf- 
Ra Again (:04) he writes: “In the Ranunculacez and 
Cruciferze studied there is not as great a difference in structure 
between cotyledons and leaves as was seen in the Papilionacez. 
ws The stalks of the cotyledon and leaf are quite different in 
anatomical structure... . . In these families as in the Papilionaceze 
there seems to be no relation in external form between the coty- 
ledon and leaf." : | 
