ON BUDS 17 



were straight, the result would be that when the young 

 leaf emerged and straightened itself the edge must 

 tear. This, however, is avoided by its being thrown 

 into folds ; and this, I believe, accounts for the lobes 

 and bays so characteristic of the Oak leaf. 



DORMANT AND ADVENTIVE BUDS 



As a rule each leaf has a single bud in its axil ; but 

 there are two other classes of buds about which I must 

 say a few words. In some species not merely one, but 

 several buds arise in the axil . They appear to have been 

 first noticed by Tristan (3). In such cases as, for in- 

 stance, the Eobinia (' Acacia ') all but one of these, after 

 attaining a certain stage of growth, become quiescent, 

 and are gradually covered over by the bark. Such 

 buds are known as ; dormant.' They may remain in 

 the same state for years, but if the growing shoots are 

 injured in the struggle for existence these reserves are 

 called into the field. Their presence is often connected 

 with that of thorns, as in Rolinia, Gleditschia, Colletia, 

 Genista, &c. ; or with tendrils, as in Passiflora. 



Another class of buds has been termed by Du 

 Petit Thouars ' adventive ' buds. They appear, especially 

 in certain plants, on the leaves, internodes, and roots. 

 They may be divided into two classes natural and 

 accidental. 



Natural adventive buds are formed by Cardamine 

 pratensis, Dentaria bulbifera, Bryophyllum calycinum, 



C 



