100 The Individual Tracks 



cell, poor in contents, divides, without at first gaining in 

 size, into a small-celled body of tissue, in which rich pro- 

 toplasmic contents can now be observed. Gradually this 

 new formation grows and differentiates, by means of nu- 

 merous further cell-divisions into a bud. 



Since these germ-tracks, which lead through a mature 

 but rejuvenating cell to a new generation, possess a high 

 theoretical value, and will be frequently mentioned in the 

 following pages, I shall give them a new name, and call 

 them fiseudosomatic. 



7. The Somatic Tracks 



As Nussbaum has so strikingly put it, the germ tracks 

 are "the continuous foundation stock of the species, from 

 which the single individuals, after a short existence, fall 

 like withered leaves from a tree." With the difference 

 that every leaf is attached to the tree at some point, 

 whereas most individuals consist of the products of nu- 

 merous somatic tracks, which have originated successively 

 from the germ-track, and therefore cannot fall off without 

 a piece of the foundation stock. 



The somatic tracks composing the individual usually 

 differ greatly from each other. Not only morphologi- 

 cally, in regard to the kind of cells, tissues, and organs to 

 which they lead, but also in their size and the extent of 

 their ramification. The whole aerial plant of Equisetum, 

 in the first year of its existence, represents a somatic 

 ramification. The leafy twigs of Tax odium, which fall 

 off in the autumn, and the leaves of all those plants which 

 are not capable of reproducing their species by means of 

 those organs, are further illustrations. There is an unin- 

 terrupted line of intermediate steps from these to the one- 



