72 Morphology BOOK i 



leaves, and the axial structures which produce them stems 

 (Characeae, Sargassum) , . . When the difference between 

 the outgrowths and the structures which produce them 

 is less ... it becomes doubtful whether the expressions 

 leaf and stem ought still to be used, and when finally the 

 similarity preponderates, the whole shoot is no longer called 

 a leafy stem, but a thallome.' Still further, he said that 

 the external differentiation of the members of the shoot 

 into stem and leaf does not depend on internal differentia- 

 tion, and instanced Caulerpa, in which such internal 

 differentiation does not exist. 



Sachs' views, therefore, were opposed to those of Wolff, 

 and his conception of the form of the plant was that the 

 fundamental differentiation of its body is into root and 

 shoot. 



As we examine Sachs' position more fully, his pro- 

 nounced physiological bias becomes more and more evident. 

 His conception of the leaf included its exogenous formation 

 from the apical meristem, and the absolute continuity of 

 the tissues there. The meristem producing stem and leaf 

 jointly is uniform. He said the leaves and the shoot axis are 

 essentially portions of one organ, the leaves being nothing 

 more than protuberances of the shoot axis, developed to 

 present the chlorophyll contained in them to the light 

 and air. He did not recognize in the veins, ribs, &c., 

 anything fundamental, like branching of an axis, as we 

 shall see some of his successors did ; he made every- 

 thing adaptive ; and discussed very fully the adaptations 

 and mechanical arrangements which they show. He 

 recognized in a typical leaf as definite regions, the lamina, 

 petiole, and sheath. 



Gcebel criticized Eichler's views in papers in the Botanische 

 Zeitung in 1880 and 1882, and modified his terminology. 

 He insisted that the two parts into which his primordial 

 leaf becomes differentiated are not sharply marked off 



