2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



favorable to germination in the absence of this compound. Appre- 

 ciably higher concentrations were required for comparable inhibition 

 if the seeds were illuminated, however.- Nutile suggested that couma- 

 rin, or related compounds, might occur naturally in lettuce seed and 

 play the role of a germination inhibitor. Coumarin, which itself does 

 not absorb visible radiation, was believed to become photosensitive 

 upon entering the seed. 



Two facts have been regarded as furnishing some support for the 

 suggestion of coumarin as an endogenous inhibitor. In the first place 

 the compound is known to occur in a considerable number of plant 

 species (see Nutile, 1945), although its presence in lettuce has not 

 been demonstrated. Secondly, a number of naturally occurring sub- 

 stances having inhibitive effects on cell growth in both plant and 

 animal tissues have been shown to possess an unsaturated lactone 

 structure as does coumarin. Coumarin has been found to inhibit germi- 

 nation and seedling development in several other species also (see 

 Audus and Quastel, 1947), although the effect of light has not been 

 investigated in these. 



Nutile's hypothesis thus seems rather attractive, and if substan- 

 tiated might contribute greatly to solution of the problem of light- 

 sensitivity of seeds. 



The present report describes some experiments undertaken with 

 the purpose of ascertaining whether the effect produced by coumarin 

 is specific for this substance or can be duplicated by other compounds 

 more or less similar in molecular structure. 



EXPERIMENTATION AND RESULTS 



Methods. — All the data herein reported relate to the black-seeded 

 variety Grand Rapids ; the seeds were of the 1944 crop and had been 

 in storage approximately 2 years at the time the experiments were 



~ As stated in Nutile's publications, the differential inhibition in light and dark 

 was found when the substrate was moistened with 10 to 100 p.p.m. of coumarin. 

 This is in agreement with our results. In an erratum supplied by Mr. Nutile it 

 is stated, however, that the actual concentrations employed were only one-tenth 

 as great as originally reported. This correction appears to have been made 

 because the solubility of coumarin is sometimes given in the literature (Seidell, 

 1941; Hodgman, 1944) as o.oi percent (100 p.p.m.), a value taken from a de- 

 termination by Dehn (1917) ; examination of Dehn's paper reveals that the de- 

 termination was of a very low order of precision. The solubility of coumarin was 

 earlier reported (Schimmel & Co., 1899) as 0.12 percent at 0° C, 0.18 percent 

 at 16-17°, and 0.27 percent at 29-30° ; we have found the solubility at 25° to lie 

 between 0.2 and 0.3 percent. 



