Adventitious Buds 99 



I should like to go further into this rich and tempting 

 field. But the reader who is familiar with the literature 

 will not need my guidance in forming a picture of the 

 secondary germ-tracks in the cell-pedigree, and in arriv- 

 ing at the conclusion that almost every larger branch of 

 this tree is to be regarded as a germ-track. 



We still have to deal with the third case, that of the 

 adventitious buds from mature cells. Here the secondary 

 tracks run through formed cells, which frequently begin 

 only in an advanced age to rejuvenate, and to grow into 

 buds. This is illustrated by the begonias, which Darwin 

 has already used in his pangenesis for the explanation of 

 the almost universal distribution of the hereditary char- 

 acters throughout all the parts of the plant-body, 16 and 

 which Sachs and Strasburger considered as opposing 

 Weismann's theory of the germ-plasm. This phenom- 

 enon has been thoroughly studied by Regel, Beyerinck, 

 and Wakker, 17 and it seems sufficiently important to me to 

 be sketched here in its main lines. 



The epidermal cells of the leaves and petioles, and also, 

 in some forms (e. g., Begonia phyllomaniacaj those of 

 the stem and its branches, possess the power of becoming 

 buds. This power is not limited to individual, privileged 

 cells, at least not in the leaves, but is inherent to the same 

 extent in all cells of the epidermis, especially in those of 

 the veins. If part of a leaf is laid on the ground in moist 

 air, after the veins have been previously cut through in 

 several places, there may be found, after some time, near 

 each wound, one or several new plantlets. The first pri- 

 mordium of these is a true rejuvenation. The epidermal 



16 Darwin, C. The Variation of Animals and Plants. 2: 362. 

 New York. 1900. 



17 See citations above (p. 98). 



