64 KENNETH V. THIMANN 



trypsin we have attempted to locate this auxin-protein in the leaves of 

 spinach, but there is more than one location. Some two-thirds of the 

 auxin is associated with a globulin in the cytoplasm, but there is also 

 much auxin in thoroughly washed intact chloroplasts. The other protein 

 preparations do not contain large amounts. The table summarizes one 

 such set of extractions. Bonner and Wildman (1946), using hydrolysis 

 by alkali, found all the auxin in a globulin, a very interesting compound 

 comprising three-quarters of the cytoplasm protein and having proper- 

 ties, including phosphatase activity, similar to those of myosin. Alkaline 

 hydrolysis does not liberate the chloroplast auxin, which explains our 

 inability to extract auxin from Lemna by alkali. Avery and coworkers 

 (1945) have reported the extraction of auxin from leaves of cabbage 

 by boiling in alkali ; but this cannot be a general phenomenon, for Miss 

 Mes, with tomato leaves (unpublished work), finds as we do with 

 spinach and Lemn-a that there is no liberation of auxin by alkali. 



Very little auxin is liberated by simple short extraction of leaves 

 with ether, i.e. very little is free in the leaf. If this relatively large store 

 of auxin in protein form were available to the plant for growth, it 

 would be expected that leaves would continue growing much longer. 

 One might expect giant cells and other evidences of high auxin con- 

 centration ; but, further, one would expect to find the auxin very readily 

 set free under natural conditions. Nevertheless many extensive experi- 

 ments which we performed with different kinds of autolysis or action 

 of autogenous enzymes succeeded only in showing a very small libera- 

 tion ; no large fraction of the auxin was ever obtained even after many 

 days' autolysis. 



A measure of the free auxin in the tissue is given by the results of 

 short-time extraction with ether, or in some cases, extraction of boiled 

 tissue with ether. Van Overbeek et al. (1945) have given evidence that 

 the free auxin is essentially extracted in two hours. From our own data, 

 based on twenty-four hours' extraction, the following figures may be 

 given for the percentage of the total auxin given up in this way, i.e. the 

 presumptive "free" auxin : 



The contrast between the two extremes is very striking, for the auxin in 



