Bd. XCV. Nr. 15. XXV. Jahrgang. 



Botanisches Centralblatt 



Referirendes Ora*an 



CD 



der 



Association Internationale des Botanistes 



für das Gesammtgebiet der Botanik. 



Herausgegeben unter der Leitung 

 des Präsidenten: des Vice-Präsidenten: des Secretärs : 



Prof. Dr. K. Goebel. Prof. Dr. F. 0. Bower, Dr. J. P. Lotsy. 



und der Redactions-Commissions- Mitglieder : 



Prof. Dr. Ch. FfahauSt und Dr. Wm. Trelease. 



von zahlreichen Specialredacteuren in den verschiedenen Ländern. 

 Dr. J. P. Lotsy, Chefredacteur 



No. 15. 



Abonnement für das halbe Jahr 14 Mark 



durch alle Buchhandlungen und Postanstalten. 



1904, 



Alle für die Redaction bestimmten Sendungen sind zu richten an Herrn 

 Dr. J. P. LOTSY, Chefredacteur, Leiden (Holland), Oude Rijn 33 a. 



Farmer, J. B., On Stimulus and Mechanism as Factors 

 in Organization. (Address delivered before Section K 

 of the British Association. Southport 1903.) 



In order to gain a wide comprehension of biological pheno- 

 mena it is essential that the factors underlying them shall be 

 convertable into chemical and physical expressions. Most 

 attempts in this direction have failed, and the hypotheses have 

 turned out to be erroneus; but the value of a theory depends 

 upon the extent to which it welds together, even tempora- 

 rily, cognate facts so as to suggest new lines of enquiry. It 

 is better to try, even if the result be failure, than to pass the 

 subject by on the other side. 



Opinions on the question are roughly divisible into two 

 classes, the one depending on the assumption that there are 

 formative stuffs present in the organism that determine the pro- 

 duction of its different parts, the other postulating the existence 

 of a quality termed „polarity". Either is insufficient. If polarity 

 means any thing, it ought to be a definite, not a variable property ; 

 but the reversal of irritable properties, as when the apex of a 

 root turns into that of a shoot (e. g. in Anthurium), seems 

 opposed to explanations based upon polarity. 



Constancy of form would seem to imply that the constituent 

 particles are he!d together by the definite and continuous Opera- 

 tion of Systems of forces, the complexity of which may depend 

 on the substances involved. The deviations round a mean form, 

 and the slight distortions of it at first sight seem sharply to 

 mark off organic shape from the definiteness characteristic of 



Botan. Centralbl. Bd. XCV. 1904. 25 



