THE ORANGE IN CALIFORNIA — DISEASES, ETC. 129 



France, and not having obtained as satisfactory results from a 

 certain test plot on wornout soil as could have been desired, 

 the writer used sulphate of iron in conjunction with the test 

 plot. The result was so satisfactory that when one of the large 

 growers of lemons and oranges last September asked what 

 remedy could be applied to prevent his trees from turning 

 yellow and much of the fruit from ripening prematurely when 

 not half grown, I suggested a liberal dose of complete fertilizer — 

 that is, one containing nitrogen, phosphoric acid, and potash — 

 together with about seventj^-five pounds of sulphate of iron 

 per acre. The orchard had previously been liberally treated 

 with stable manure, yet some of the trees were not in a healthy 

 condition. Now the trees have a health}^ green appearance, 

 and nearly if not quite all of the new growth is of a bright or 

 deep green color, whereas the trees that were not treated have 

 the new growth showing a variegated, streaked leaf. Since the 

 first experiment was tried several other plots have been treated 

 in the same waj^ with the most gratifying results. As to the 

 why and wherefore of the encouraging results obtained from 

 the use of sulphate of iron, we confine ourselves to quoting 

 what Dr. Griffiths says upon the subject: 



"'Three years' experiments show that a small dressing of a 

 hundredweight of iron sulphate per acre is a most beneficial 

 manure. 



'"The author's proposition (Chemical News, A^ol. XL VII, p. 

 27) was that a "fairly large proportion of soluble iron in a soil is 

 favorable to the growth of plants developing a large amount of 

 chlorophyll." And all subsequent investigations on the growth 

 of crops with iron sulphate have entirely confirmed the 

 accuracy of that proposition. 



'• 'All soils contain iron as a constituent, but the iron is not 

 always in a form to be readily taken up by growing crops. 

 This being so a crop must suffer, iron being one of the ingre- 

 dients requisite for the formation of green chlorophyll. 



" 'Chlorophyll is a substance of primary importance in every 

 plant (giving rise in the first instance to starch, woody fibers, 

 fats, and carbohydrates generally); therefore it is necessary to 

 add soluble iron compounds, where the soil is deficient in these 

 ingredients, or where the iron is not in a form for root-absorp- 

 tion. Some soils are certainly deficient in soluble iron, and -no 

 , 9c 



