232 Journal of Agricultural Research voi. 111.N0.3 



maturity, there is throughout the development of the seed a gradual and 

 rather uniform gain in the oil content as compared with the growth of the 

 seed. There is no evidence of a definite " critical period " for the accumu- 

 lation of oil during the development of the seed. Considering only the per- 

 centage of oil, there is a very sharp increase during the first few weeks after 

 blooming, and then only a slow gain until near the end of the ripening. 

 During the final stage of ripening there is a decrease both in the size of 

 the seed and in the oil content. This phenomenon, which was observed 

 also by Miintz (1886), is probably due to continued respiratory activity 

 after assimilation has ceased. In the case of the cotton seed the immature 

 samples were taken when the green bolls had reached full size and had 

 begun to show numerous brown spots. As in soy beans, the increase in 

 oil proceeds somewhat more rapidly than the growth of the seed. 



OIL CONTENT OF SEED AS AFFECTED BY RATIO OF LEAF SURFACE TO 

 QUANTITY.OF SEED PRODUCED 



It has been shown that the accumulation of oil in the seed proceeds 

 throughout the greater portion of the period of development and ripening. 

 It also has been pointed out that during the so-called vegetative period 

 preceding blooming there is an accumulation of carbohydrates in the 

 leaves and stems which is later utilized in the formation of the oil deposited 

 in the seed. From these facts it might be inferred that the total quantity 

 of oil stored in the seed would be affected by the relative extent of the 

 photosynthesizing plant parts, more particularly the leaves, while, on the 

 same basis, the percentage content of oil might be influenced by the ratio 

 between the photosynthesizing parts and the quantity of seed produced. 

 In other words, it is to be expected that premature shedding of leaves, 

 such as often happens under adverse conditions, or the shedding of a por- 

 tion of the blossoms would affect the accumulation of oil in the seed. As 

 regards the quantity of seed produced, a diminished supply of accumu- 

 lated carbohydrate might lead to the production of a smaller number of 

 seeds or of smaller sized seeds, or possibly both. 



For the reasons indicated it is apparent that in any analytic study of 

 oil production in the seed as related to factors of nutrition account must 

 be taken of the possible effects of the nutrition conditions during the two 

 principal life periods of the plant — namely, the vegetative and the repro- 

 ductive. The production of oil by the plant requires favorable conditions 

 for the accumulation of carbohydrate during the vegetative period and 

 for the transformation of carbohydrate into oil during the second period, 

 although there may be, of course, more or less overlapping of the two 

 processes. As a special phase of the influence of the accumulation of car- 

 bohydrate on oil fonnation, experiments were carried out with soy beans 

 in which the normal distribution of the vegetative and reproductive plant 

 parts was modified by partial defoliation and by removal of a portion of the 

 blossoms or very young seed pods. The number of plants used in each 



