44 



I. NAG.U: 



The puiple iiud reel a^\n is greeu wlieu the panicle is iu the leaf-sheath. 

 The red colour begins to develop at fii'st at the tip and the base of tha awn, 

 a day or two after the panicle has appaared from the leaf-sheath (see Plate 

 I). The colour gi'adually extends to the entii'e portion and at the same time 

 increases in intensity. The pm'j^le awn is red iu the beginning, but rapidly 

 inteusifies in ce)lour and becomes deep piu'ple. In the red awn, on the other 

 hand, the red pigment remains unchanged and sooner or later, it is decomposed. 

 A similar change is obssrved in the glume. 



The development of the pigment in the awn is depaudent on the illumi- 

 nation. When the panicle .is enclosed in the papar bag to ensm-e self pallinji- 

 tion, the pigment develops only slightly. In th^ stigma, purjjle anthocyanin 

 is ah-eady present even when the p.anicle is still in the leaf sheath. Tims 

 the development of anthocyanin is saen to have difierent physiological requii'e- 

 ments even iu ths difi(?rent parts of the same floral organs. 



In the cells of the colourless stigma, flavone c:m be detected by ti'eating 

 them with ammonia which jield a deep yellow colom-. It is quite probable, 

 however, that there may be a colourless stigma having no flavone (chromogen). 

 Hector (1916)' has shown that the colour of stigma in certain cases, is due 

 to more than three factoi-s. 



Tlie anthocj-anln pigment in tlie palea is coufinal to the epidermis, and 

 the brown pigment to the underlying tissue. The brown pigment is practically 

 insoluble in strong alcohol, but slightly iu a weak solution. Fully matural 



* The colour indistinct, sometimes obscure. 

 1. Hectob, Ci. P., Loc. cit. 



