May 20, 1918 Chemistry and Histology of Glands of Cotton 423 



it is wholly or nearly insoluble. In alkalis the globules swell, become 

 orange in color, and dissolve, forming a bright-orange solution which 

 becomes yellow on dilution. A dark-green precipitate is formed by alco- 

 holic ferric chlorid, and an orange or yellow precipitate by lead acetate. 

 These reactions are characteristic of flavones. Quercetin and several of 

 its glucosids have been shown by Perkin (9, 10, 11) to be present in the 

 cotton plant, and a previous paper {17) from this Bureau discusses the 

 isolation of quercetin and two of the glucosids, quercimeritrin and iso- 

 quercetin, from the flowers and foliage of the species here considered. 

 The latter glucosid was present only in very small amount. The reac- 

 tions of these substances correspond well with those of the yellow globules 

 of the glands, and no reactions of flavones have been noted in other por- 

 tions of the green parts. 



SECRETIONS OP GLANDS NOT EXPOSED TO LIGHT 



The secretion of the young glands which are not exposed to light also 

 consist of a yellow fluid, with a slightly greenish tinge. In a mature or 

 dried gland it becomes hardened into a reddish-resinous solid. It differs 

 from the secretion of the glands mentioned in the preceding paragraph 

 in forming a greenish emulsion with water and aqueous reagents. It is 

 soluble in alcohol, ether, acetone, and chloroform, but is insoluble in pe- 

 troleum ether and xylene. Its behavior with alkalis is similar to that of 

 the secretion of the illuminated glands. The chief reaction by which it 

 may be identified within the gland is an intense red coloration induced 

 by concentrated sulphuric acid, which reagent dissolves quercetin and 

 its glucosids with more or less difficulty, forming a yellow solution. 

 This red reaction, first noted by Hanausek (5) was cited by Marchlewski 

 (7) as a property of gossypol, which Withers and Carruth (jp) consider 

 to be the toxic agent in cotton seed. This red reaction is characteristic 

 of all stages of the glands of the seed and secondary cortex, but is absent 

 in those of the primary cortex and foliage. Glands of the developing 

 petal at first give the gossypol-red reaction, but before or soon after the 

 petal unfolds they lose this property and react as the glands of the green 

 parts. Synchronously with this change of character occurs the develop- 

 ment of anthocyan in the enveloping cell layers. A strip of petal may 

 show all gradations from intense red to yellow reactions with sulphuric 

 acid, according as the glands have been exposed to the light. These 

 changes were clearly marked in blossoms of G. barbadense, and were con- 

 firmed in field-grown specimens of G. hirsutum. No gossypol was re- 

 covered from 800 gm. of ground, dried cotton flowers by the method by 

 which Withers and Carruth (19) isolate the substance from cottonseed 

 kernels. Their process consists in precipitating gossypol from the ether 

 extract by petroleum ether. 



Glands of blossoms of the Upland cotton plant which had been grown 

 in a greenhouse whose roof was so heavily painted as to prevent largely 



