ON PLANT GROWTH HORMONES 603 
bond, and it is at acarbon atom bearing this double bond that the C;-residue 
is attached. 
I will not present here probable formule for auxin which may seem rather 
premature ; but I will limit myself to a few formule which by now have 
6uplanation of degradation. 
results : 
"Cotes 
4 Coonpea ase? Seni, 
Cy -mesidue : 
—CL CH-Ch- CH Coow- 
. "lactone w 
3, C,-restdue : ane 
—G 
4, OxCdation ofauxin: 
: Ee oir Meany Cog COOH 
A ND (Fe) 
3; Quidation of difydro anvin : 
CF rb Gz C008 
Me ro, C0 (tind) 
Fic. 5. 
already been disproved but nevertheless afford an illustration of the con- 
stitutional problem. Attention may first be called to the formula of chaul- 
moogric acid (Fig. 6). Like auxin this vegetable acid contains 18 carbon 
atoms, a double bond, and a ring ; there is, however, no relationship, for 
chaulmoogric acid has a terminal ring. Of the formule in Fig. 7, the first 
may be excluded with certainty since 4-m-heptyl cyclo hexanone, synthesised 
by Mr. Picard, is not identical with our ketone. The exact comparison of 
B-n-heptyl adipic acid, which was also synthesised, has not yet been made, 
=CH 
(TS cHe- (Ct COOH: 
Cte —Ch 
chaulmoogric acid 
(Cratt20) 
Fic. 6. 
since the synthetic acid has not yet been resolved into its enantiomorphs ; 
the same applies to «-n-heptyl adipic acid synthesised by Mr. Koningsberger. 
The following experiments showed us, however, with certainty that our 
C,;-acid has a different structure, for we submitted the two adipic acids, 
in quantities of 20 mg., to Blanc’s reaction and could obtain definitive 
evidence of the formation of pyrolytic ketones. The degradation product 
however furnished in a similar experiment no such ketone, but an acid 
anhydride. The formation of an anhydride in Blanc’s reaction is quite 
general with glutaric acids, exceptional with adipic acids. Hence we con- 
sider it to be more probable that our degradation product is a glutaric acid 
and that auxin contains a five ring. Numerous substituted glutaric acids 
