﻿4 BULLETIN 1HG, D. S. DEPARTMENT OF AGRICULTURE. 



Pott (37) showed that the water content decreased, while the 

 total nitrogen, starch, and crude fiber contents increased in the tubers 

 as they matured. 



Prunet (39) considered that during growth the nutritive sub- 

 stances are uniformly distributed in the tuber, but after full size has 

 been reached there is a movement of these substances toward the 

 apical buds. 



Jones and White (24) in 1899 reported some experiments made on 

 Delaware and White Star varieties of potatoes in Vermont. From 

 analyses of tubers from both Bordeaux-sprayed and unsprayed plots, 

 they concluded that the variations in yield were of more importance 

 than variations in composition. The unsprayed tubers showed the 

 presence of more water and ash than the sprayed tubers. As all- of 

 the tubers matured the solids and nitrogen-free extract decreased 

 somewhat, while the ash, protein, and crude fiber increased slightly. 



Stewart. Eustace, and Sirrine (46) in 1902 reported that one lot 

 of tubers from Bordeaux-sprayed plants gave higher solids and 

 starch results than a corresponding lot from unsprayed vines. 



Woods (51) of the Maine station in 1919 published analyses show- 

 ing that tubers from Bordeaux-sprayed potato vines averaged 19.1 

 per cent starch and that tubers in the same field from unsprayed vines 

 averaged 17.5 per cent starch. The dry matter in the tubers from the 

 sprayed portions of the field was also \\ per cent higher than that 

 in the tubers from the unsprayed portions. 



PLANTS IN GENERAL. 



Sorauer (45) observed that swellings were formed on the leaves of 

 potato plants b} T the action of copper salts. Sections of these 

 growths showed that they were composed of parenchyma cells so 

 strongly hypertrophied as to break the epidermis. 



Frank and Kriiger (19) in 1894 obtained a definite improvement in 

 growth by treating potato plants with a 2 per cent Bordeaux spray. 

 The effect of the copper was most marked on the leaves and was 

 chiefly indicated by plrysiological activity rather than morphological 

 changes. The leaves were thicker and stronger and their life was 

 lengthened. The chlorophyll content was apparently increased and 

 correlated with this was a rise in the assimilating capacity, more 

 starch being formed. A rise in transpiration also occurred. A sub- 

 sidiary stimulation took place in the tubers, as the greater quantity 

 of starch produced required space for its storage. The ratio of tuber 

 formation on treated and untreated plants was 19 : 17 and 17 : 16. 

 These investigators held that the action was catalytic, that is, an 

 increase in photosynthesis resulted from the presence of copper. 



Ruruni (40) in 1895 noted that grape foliage sprayed with Bor- 

 deaux showed thickened leaves of a blue-green color which outlived 

 the leaves of the unsprayed vines. After measuring leaves from 

 sprayed and unsprayed vines Eumm presented data showing that the 

 thickness of the leaf, the epidermis, the palisade tissue, and the 

 parenchyma was increased in the case of the sprayed vines. These 

 data suggest that copper was taken into the growing leaf where it 

 produced certain morphological changes. 



Lodeman (31) found that the thickness of plum leaves and prune 

 leaves was increased by the application of Bordeaux spray. 



