E. H. NEWCOMB 4-^ 



(i) the petals of certain flowers which have been investigated show the 

 greatest epidermal oxidase activity in the most deeply colored varieties, 

 less in the less deeply colored, and none at all in the white varieties. 



Higher oxidase activity in galls than in unaffected tissue has been re- 

 ported by several workers. Using the benzidine reaction. Parr (i8) 

 found much greater activity of oxidases in the gall tissue than in the 

 normal oak stem tissue. The oxidases increased in activity in the gall dur- 

 ing the growth period and then diminished. With decreasing oxidase 

 activity in a region of the gall, the tannin content of the region increased. 

 MoUiard (12) reported increased laccase and tyrosinase activity in two 

 elm leaf galls. Quantitative data obtained by the writer, presented in 

 detail below, show a several fold increase of tyrosinase activity in the 

 grape phylloxera gall during its development. 



Increased oxidase activity has also been shown for bacterial galls. 

 Nagy and Riker (13) found that the oxidase, catalase, and peroxidase 

 activity of tomato crown gall tissue is 130, 160, and 120 per cent greater, 

 respectively, than for the contiguous tissue, on a fresh weight basis. 



Nierenstein has discovered that the striking colorations of insect 

 galls are due to glycosides of a derivative of gallic acid, itself a constituent 

 of tannin. It had been assumed that the gall pigments are anthocyanins, 

 but in 1919 Nierenstein (14) reported that the pigment of a Cynipid gall 

 on oak leaves is a glycoside of purpurogallin. The latter, which had not 

 been reported elsewhere in nature, has the following formula: 



Nierenstein and Swanton (16) have shown that the pigments of a large 

 variety of galls, caused by such diverse organisms as insects, mites, 

 roundworms, and fungi, are all purpurogallin glycosides. All glycosides 

 investigated yielded two glucose residues on hydrolysis. Since four 

 biglucoside isomers are possible by attachment to one or another of the 

 four hydroxyl groups, and two glucose residues can occur on each of 

 two different hydroxyl groups in six different combinations to give six 

 additional isomers, there are ten possible isomers. Eight of these were 

 isolated from galls, crystallized, and distinguished chiefly on the basis 

 of differences in melting points. 



