ORGANIZATION AND GROWTH 207 



theory of organization. 1 Sachs assumes that "with differ- 

 ences in the forms of organs are connected differences in the 

 substances composing them," and that "from principles 

 which hold for all sciences we must assume that the differ- 

 ences must be derived causally from the differences in 

 chemical constitution" (p. 425). "We shall have to assume 

 the existence of just as many specific formative substances 

 as there are different forms of organs in the plant." The 

 specific morphogenetic substances are affected through 

 external conditions, especially gravity and light, "so that in 

 certain cases the spatial arrangement of the different organs 

 is determined thereby." The monstrous formation of an 

 organ at the place where normally another organ should 

 exist as in the case of heteromorphoses Sachs attributes 

 to an absence of the specific substances necessary for the 

 formation of the normal organ at this place, and the presence 

 instead of the specific formative substances of another organ 

 (p. 464). Sachs also explains why any regeneration what- 

 soever of roots or stems occurs in plants deprived of them. 

 "Why is it that the simple removal of a piece calls forth a 

 regeneration of organs at places where this never would 

 have occurred without some disturbing influences such as 

 the removal of the piece?" (p. 470). The answer is as 

 follows : 



I assume that as long as a green-leafed plant with an upright 

 stem is nourished and growing, the specific formative substances 

 for the root flow from the assimilating leaves to the system of roots 

 at the lower end of the stem, while the substances forming the stem 

 flow in a similar manner upward toward the growing points of the 

 stem and the branches. If a piece is cut out of the stem or the 

 root, the cut surface in itself offers a barrier to the further move- 

 ment. The specific formative substances contained in it will, in 

 consequence, collect in the neighborhood of the two cut surfaces. 

 Those substances leading to the formation of roots will collect at what 



i J. SACHS, Arbeiten des botanischen Institute in Wiirzburg, Vol. II (Leipzig 

 1882) , pp. 452, 689. 



