i9o8] SCHREINER c^ REED—TOXIC PLANT CONSTITUENTS 91 



eight days, but all growth had ceased. The root tips were discolored 

 and badly swollen. The leaves were dead for a considerable distance 

 back from the tips. In the solution of i ppm. the development of 

 tops, as shown by the illustration (fig, 6), was practically equal to 

 that of the control plants in distilled water. The root development 

 was not as good, however, the tips being slightly discolored but not 



swollen. 



Daphnetin, which occurs in various species of Daphne, is a lactone, 

 which is to be regarded as (3, 4) dioxycumarin. On account of its 

 slight solubility in water it was impossible to test daphnetin in con- 

 centrations greater than 50 ppm. Daphnetin was relatively less 

 toxic than cumarin. At a concentration of 50 ppm. the green weight 

 of tops produced m twelve days was 76 per cent, of the controls. 

 In concentrations of 25 ppm. and less the growth of tops was prac- 

 tically as good as in distilled water, and the development of roots was 



only slightly inferior. 



Esculm is of particular interest on account of its relation to cumarin. 

 It is the glucoside of esculetin, which is a lactone isomeric with daph- 

 netin, and has been shown by TiEirA>rN and Will ('82) to be (4, 5) 



.ma 



Both esculin and esculetin have been found in plants, but little is 



■ tVtpir Hktrihiition. The esculin solutions had a 



:rmn 



blue fluorescence when prepared, which was lost after plants had 

 gro^-n for a time in them. The roots which grew m the stronger 

 solutions were colored dark yeUow as a result of their oxidative acti\i- 

 ties, the dye formed being insoluble and remaining upon the surfaces 

 of the roots where oxidation had occurred. This effect is sho^^m m 

 fig. 7. Esculin, as sho^-n by the figures, is decidedly less toxic to 

 plants than cumarin, but more toxic than daphnetin. Klebs ( 90) 

 found that a saturated solution of esculin inhibited the formation of 

 zoospores in Con]erva minor^ but did not pre.-ent the formation of 

 chlamvdospores in Miicor racemosus. The toxic effects of escubn 



^eat 



III concentrations of looo and 500 ppm. wheat plants were Ml. 

 and were injured even in a solution containing i ppm. (fig. 7h 

 the solutions containing 100 ppm. there was a distinct stimulation 

 the growth of tops. 



In 



