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.^^ The line of de- 

 marcation between the secondary germ-tracks and the 



i^This point indeed still requires thorough investigation. 



