Secondary Germ-Tracks 97 



The second group of secondary germ-tracks, the ad- 

 ventitious buds from meristematic tissues, is by far the 

 most widely distributed in the vegetative world. Adven- 

 titious buds arise in part directly from the normal meri- 

 stematic tissues, in part throught the medium of the cal- 

 lus-tissue which leads to the closing up of wounds. 

 Those that originate from stems or branches, usually 

 become new twigs of the individual bearing them, the 

 leaf-born ones and the root-buds, however, develop for 

 the most part into new plantlets. 



Bud-formation from callus is chiefly found in woody 

 plants, and almost every part of a branch or a root, if cut 

 for a slip or otherwise injured, can develop from the 

 youthful cells of the cambial zone, situated between the 

 wood and the bark, that undifferentiated tissue, oozing 

 out like drops of a semi-fluid substance, in which later 

 cork, bark, and wood, as well as the rudiments of numer- 

 ous buds develop. According to circumstances the buds 

 become roots or leafy twigs, and usually replace the lost 

 members of the individuals. 



Since, as far as we know, every cell of the cambium 

 may contribute to the callus, and can produce therein the 

 mother-cell of a bud, we must designate the entire cam- 

 bium as a secondary germ-track which is as profusely 

 ramified as the cell-pedigree of the respective cambium 

 itself, and which bears the normal products of its activity, 

 wood and bark, as countless somatic twigs. It is to be re- 

 membered, however, that many cells of the wood and bark 

 retain, for a longer or shorter time, the power of con- 

 tributing to the formation of the callus, and even of pro- 

 ducing mother-cells of callus-buds. 13 The line of de- 

 marcation between the secondary germ-tracks and the 



13 This point indeed still requires thorough investigation. 



