164 Journal of Agricultural Research voi.xxi,No. 3 



work on chlorosis lies in the domain of the biochemist rather than of the 

 pathologist or the forester. 



The immediately practical applications are fortunately simpler. The 

 writers have added three gymnosperms to the considerable list of angio- 

 sperms in which chlorosis can be relieved by spraying ferrous sulphate on 

 the surfaces of the leaves. While the best way to avoid chlorosis in co- 

 niferous nurseries is probably to avoid soils containing any considerable 

 quantities of calcium carbonate, an entirely practicable method of treat- 

 ment is offered by which chlorosis can apparently be relieved in coniferous 

 nurseries on lime soils. At the rate at which the experimental spraying 

 was done, using the i per cent solution, which on the whole gave the best 

 results, i pound of the relatively cheap ferrous sulphate is sufficient for 

 over 900 square feet of bed. While with larger stock more material 

 would be required, the process would still be relatively cheap. Johnson 

 (jo), using a solution eight times as strong, reported the total cost of 

 spraying pineapples as $0.60 per acre for each spraying. In a business 

 as intensive as that of raising coniferous nursery stock such a cost item 

 would be almost negligible. 



RELATION BETWEEN CHLOROSIS AND GROWTH 



Observations through several seasons at the Pocatello Nursery have 

 indicated a relation between chlorosis and poor growth. In order to 

 secure data on this relationship the seedlings in the control plots whose 

 counts are given in figure i were classified by their apparent vigor of 

 growth as well as according to their chlorotic condition. The counts 

 showed for the first series that 23 per cent of the seedlings classed as vig- 

 orous were chlorotic, while 42 per cent of the weak seedlings were in the 

 chlorotic class. For the second series the difference was about the same, 

 46 per cent of the vigorous seedlings being chlorotic against the very 

 high proportion of 73 per cent among the seedlings classed as weak. In 

 an effort to put this relationship on a more exact basis, specimens were 

 selected from each class and subclass of seedlings of which a sufficient 

 number were available to give a reasonable numerical basis, and measure- 

 ments of roots, stems, and leaves were made. 



METHODS OF SECURING MEASUREMENTS 



The seedlings taken were selected by a process of mechanical elimina- 

 tion, every fifth seedling being chosen in most of the cases, so that they 

 are believed to be representative of the groups from which they came. 

 The leaf surface values were obtained by a method which does not pre- 

 tend to give the absolute surface accurately, but which is believed to 

 give sufficiently accurate relative values to permit a comparison of the 

 different groups of plants. 



The surfaces of the primary and secondary leaves of western yellow 

 pine were determined separately on account of their different shapes. 



