70 J. K. POLLARD 
- ACETIC 
BUTANOL 





RHE NOL 
+p SRO 
Fig. 1B. For legend see p. 69. 
4C-urea. The second is that if the substance in question had not been radioactive, the 
variety of compounds to which it may give rise in the medium would never have been 
detected. 
Consequently, in studies of this sort, care must be taken to evaluate the effects of 
autoclaving on the actual composition of the final medium which is used in tracer 
experiments. 
REFERENCE 
1 R. F. Lynpon, J. K. PoLLtarp anp F. C. StEwarpD, Plant Physiol., Suppl., 34 (1959) xx. 
