May 2,i93i Effect of Ferrous Sulphate on Chlorosis of Conifers 165 



FIG. 4. Cross-sectional 

 shape of fascicle of three 

 secondary leaves of western 

 yellow pine. 



The primary leaves are approximately semicircular in cross section, and 



for the purpose of obtaining a comparative surface value were considered 



as halves of cylinders having a radius equal to the thickness of the 



leaf midway between the base and the tip, with the length equal to the 



length of the leaf. The perimeter of the cross section at this point was 



taken as xR + 2R that is, the sum of the lengths of the curved and 



the flat margins of the cross section. The surface of the leaf was 



taken as S = L(7rR+2R), in which L, equals the length of the leaf. 



A sufficient number of primary and secondary 



leaves from each plant were measured to allow 



averaging (usually from 25 to 100, depending on 



the number per plant) . The total primary leaf 



surface for the plant was obtained by multiplying 



the surface of the average leaf by the entire 



number of primary leaves. The secondary leaves 



were in most cases in fascicles of three, and their 



cross-sectional shape may be diagrammed as in 



figure 4. The same assumptions were made in 



this case as in the case of the primary leaves, 



the leaf being taken as an exact third of a 



cylinder with the radius equal to the thickness of the leaf midway 



between the base and the tip, and the surface calculated by the formula 



S = I/ - - 4- 2R 



a paraboloid formula, and it is believed that it offers a better basis for 

 comparing the leaf surface of one group of plants with that of another 

 than would be given by statements of the average number, length, 

 breadth, and thickness of the leaves. 



INTERPRETATION OP THE MEASUREMENTS 



From Tables III and IV it appears that the height and the weight of 

 the tops, the length and the weight of the roots, the diameter of the 

 stems at the root collar, the length and thickness of the secondary 

 leaves, and the average total leaf surface of the plants was less for 

 chlorotic plants than for green seedlings of the same vigor class and that 

 terminal bud formation was most common and most pronounced in the 

 most vigorous plants. The data indicate that the failure to form buds 

 is related to a general lack of vigor, which in many cases is associated 

 with chlorosis. The adverse effects of chlorosis on terminal bud forma- 

 tion and development is significant in connection with the high winter 

 mortality of the strongly chlorotic seedlings. 



The small size of the different parts of the plants in the chlorotic 

 seedlings, as compared with the green seedlings, is, on the whole, fairly 

 uniform. Two exceptions to this are, however, noteworthy. In Table 

 III it appears that the roots of the chlorotic plants are nearly as long 





This formula appears to be more nearly correct than 



