98 The Individual Tracks 



somatic tracks is therefore to a great extent, obliterated 

 here, and perhaps even quite undemonstrable. 



Callus-buds are also to be found in many herbaceous 

 plants. On leaves, too, they are not rare, but in such 

 cases they usually form new rooted plantlets. 



Adventitious buds on leaves are very frequent phe- 

 nomena among the ferns. In the phanerogams they arise 

 at the base of detached leaves, especially in bulbous plants 

 and Crassulacese. Very well known instances are fur- 

 ther furnished by Bryophyllum calycinum, Cardamine pra- 

 tensis, and Nasturtium officinale. There can be no doubt 

 that in all of these cases there is present in every leaf 

 a germ-track, which is very frequently much ramified. 



Root-buds are probably the most common and cer- 

 tainly the most completely and most thoroughly investi- 

 gated adventitious buds. 15 And since many leaves, like 

 slips from stems and roots, can form roots after having 

 been detached from the plant and, by means of these 

 roots, give life to new plantlets, the importance of the root- 

 buds can hardly be exaggerated. Many plants, such as 

 Monotropa, multiply, except by seed, only in this manner, 

 others, like Rumex Acetosella and the thistles become the 

 most tenacious weeds by means of root-buds. Of all spe- 

 cies that possess this power, we can therefore say that 

 their root-system represents, in the cell-pedigree, a much 

 ramified germ-track with its somatic twigs. 



14 From the abundant literature on this subject I cite: Regel, 

 Vermehrung der Begonien aus ihren Blattern. Jenaische Zeits. 

 Naturw. p. 478. 1876. Beyerinck, Over het ontstaan van knoppen en 

 wortels uit bladeren. Ned. Kruidk. Archief. 3: 1. 1882. Wakker, J. 

 H. Ondersoekingen over adventieve knoppen. Amsterdam, 1885. 



15 This subject has been most exhaustively treated by Dr. M. W. 

 Beyerinck in his "Beobachtungen und Betrachtungen iiber Wurzel- 

 knospen und Nebenwurzeln." Verhandl. Kon. Akad. Wetenschappen. 

 Amsterdam, 1886. 



