264 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



group are very slight, yet many of the flowers are deeply 

 pigmented with anthocyanin; furthermore, attempts to 

 find more marked reactions in unopened buds, which are, 

 of course, shielded from intense sunlight, only resulted in 

 further confirmation of the behaviour of the mature flowers. 



EFFECT OF ABSENCE OF LIGHT UPON THE PEROXIDASE 

 OF IRIS FLOWERS. 



As already mentioned, Keeble and Armstrong (1912, 3) 

 found the quantity of peroxidase and of organic peroxide to 

 have increased in flowers kept in the dark. Before con- 

 cluding definitely that the reactions of Iris flowers had the 

 meaning attributed to them viz., that they were genuine 

 expressions of the properties of particular species and 

 varieties it was necessary to inquire into the possibility 

 that they might have been in part due to differences in 

 illumination. With a view to testing this, the Irises men- 

 tioned in Table LXII. were picked at 5 p.m. on a hot sunny 

 day in July. Of each flower, one of the falls was removed 

 and examined immediately. The reactions afforded by 

 these are given in column No. 1. The flowers were then 

 placed in total darkness, with their stalks in water. After 

 twenty-one hours the second of the falls was removed, and 

 the third after sixty-six hours. The behaviour of these is 

 shown in Nos. 2 and 3 respectively. In the table, + refers 

 to the whole of the fall, unless a portion such as the claw 

 is mentioned. Thus, " + claw " indicates a less general 

 distribution than does + alone. The reagent employed 

 was a-naphthol, as it is more selective in its action than is 

 benzidine 



It is at once evident that the absence of light permits of 

 the accumulation of peroxidase in active condition, and 

 even leads to the formation of organic .peroxide in the 



