THE COTYLEDONS AND LEAVES OF CERTAIN 

 PAPILIONACEAE 



By Francis Ramaley 



Nature of the Cotyledon. The view that cotyledons are to be 

 considered as leaves has long been held and botanists and others are 

 accustomed to speak of cotyledons as "seed leaves." Such a con- 

 ception is natural enough from a mere examination of external 

 appearances. Doubtless Goethe's doctrine of metamorphosis, which 

 has dominated much of the botanical teaching of the past, is also 

 partly responsible for this view. But although the cotyledons have 

 been referred to as "seed leaves" the differences which they ehow 

 have been frequently noted. A recent suggestion by Lyon^'^ is that 

 the cotyledon was originally a haustorial organ which became modi- 

 fied for purposes of storage and, in some cases, becoming epigean 

 through the elongation of the hypocotyl, took on the appearance and 

 function of a foliage leaf. According to this view similarity of 

 cotyledons and foliage leaves has been brought about through adap- 

 tation to similar conditions of life but the two structures are 

 essentially different. The haustorial nature of the cotyledon has 

 been referred to recently by Thistleton-Dyer,<^' and others, and has 

 doubtless been recognized by many botanists. Thistleton- Dyer's 

 recent suggestion of the value of anatomical study of cotyledons 

 has led to the publication, at this time, of the results of some studies 

 which have been carried on by the writer during the past two years. 



Material. Seedlings were grown of a considerable number of 

 Colorado Papilionaceae. These were taken at different periods of de- 

 velopment and preserved in alcohol. A large amount of similar 



(1) Lyon, in Postelsia, 57-86. 1902. 



(2) Thistleton-Dyer, in Ann. of Bot., 16: 553. 1902. 



