Chemistry and Qrowth 



those of workers who have tested the action of the derivatives 

 on plants, and are not necessarily those of the synthetizers. 

 Thimann's coumaryl-acetic acid was called the i-acid by 

 him, as he excepted the oxygen atom from numbering. It is 

 substituted in the same position as is the better-known 

 coumarilic acid, called coumaryl-2-carboxylic acid by 

 Heilbron (1934).^ 



Shackell (1937), who reported the preparation of ^thio- 

 naphthene-3 -acetic acid (by whom, is not clear, but see also 

 the paper by Crook and Davies (1937) ) found that compound 

 inactive in the Avena (oat) test of coleoptile bending, but 

 active in fairly high dilution by Went's etiolated pea method 

 (see p. 129). 



Thimann's results are most succinctly given in the form of 

 a table, which also brings out the typical difference in activities 

 revealed by different methods of assay, thus suggesting how 

 much caution should be brought to attempts to correlate 

 chemical constitution with an unspecified "activity". 



Table. — Approximate Activity expressed as Percentages 

 OF that of Indole-3-acetic Acid. (Thimann (1935) ) 



^ The opportunity has been taken of correcting some mistakes v^^hich 

 were made in Part III of the article in the Manufacturing Chemist (August 

 19:^7) before the author had access to the original of Thimann's 1935 paper. 



* True naphthenes are C2H2n. Thionaphthene is analogous to indene 

 and indole, but the name thio-indene is not, however, sanctioned by custom, 



* Dependent on mode of application, etc. 



83 



