172 SCIENCE PROGRESS. 



experimental morphology ; deformities, galls, etc., could be 

 referred to definite changes of substance ; and the as- 

 sumption that stem-forming substances find their way to the 

 point of stem-growth, root-forming to that of the root- 

 system, explained to him most naturally the facts to be 

 seen in reproduction. It is evident that in such a difficult 

 subject one must look for sketches, or general views, rather 

 than theories worked out in detail. But at any rate Sachs' 

 views are more fruitful than Nageli's " Idioplasma," and he 

 made a number of experimental morphological studies on 

 their bases. 



He had already arrived at the conception of the conti- 

 nuity of the embryonic substance before the appearance of 

 Weismann's Germ-plasm. " That which has maintained 

 itself alive, and has continually reproduced itself since the 

 beginning of organic life upon the earth, moving steadily 

 onward in the eternal change of all structures, in the un- 

 varying alternation of life and death, that is the embryonic 

 matter of vegetation and it is this which in certain cases 

 differentiates itself into the two sexes in order again to 

 unite." 



He conceived of the multiplicity of plant forms as arising, 

 on the one hand, from the phylogenetic morphological 

 differentiation (this, however, he regarded as an " absolute 

 mystery "), and on the other from the re-action of the 

 common vegetable substance in response to external stimuli 

 (automorphosis and mechanomorphosis). "Adaptation" in 

 Darwin's sense of the expression he considered entirely 

 superfluous, and herein he was in entire agreement with 

 Nageli. He expressed his views in a powerful manner in 

 his last, writings — the physiological "Notices" 1 published 

 in "Flora". The manuscript found after his death, en- 

 titled "The Principles of Vegetable Formation," has been 

 handed, over to Prof. Noll for publication. 



This slight sketch can give but an inadequate idea of 

 Sachs' lifework with its abundant results as regards science ; 

 indeed I can but liken what I have written to a man striking 



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1 These will shortly appear as a separate publication. 



