ON THE STRUCTURE OF BUDS 115 



4. Another strong reason for regarding the outer 

 sheath as representing a pair of leaves is that it 

 is more or less carinate on the edges, right and left 

 that is, laterally. The inner face shows a number 

 of longitudinal, parallel nerves, the two strongest of 

 which occupy the position of the carina or keel, and 

 correspond to the midribs of the two leaves. The mid- 

 ribs being right and left of the bud, agree with the 

 insertion of the first two leaves of axillary buds, those 

 leaves being generally at right angles to the leaf on the 

 main axis. 



A curious case occurs in Salix cordata, S. lucida, 

 and 8. lanata. The inner membranous face of the 

 scale separates more or less completely from the coria- 

 ceous outer one, and resembles a second scale. It is, 

 however, exactly opposite to the outer layer of the scale 

 (not alternate), and is divided in the same way as the 

 outer layer. 



Perhaps, however, the strongest reason for regard- 

 ing the outer sheath as composed of a pair of leaf- 

 blades is that we often find a pair of buds at the base. 

 Lindley l quotes this as showing that stipules occasionally 

 develop buds at their base. It seems more reasonable 

 to regard the fact as evidence that they represent 

 leaves, and not merely stipules. 



It is remarkable that while in the Poplars (Pojmkts) 

 the buds are protected by the stipules, in Salix the 



1 Introd. to Botany, p. 99. 



i *2 



