898 Miller. — A Physiological Study of the 
The large amount of soluble acids in the neutral oil of the cotyledons in 
Stage VI indicates that there are present considerable quantities of the 
glycerides of the lower fatty acids. The quantity of soluble acids in the 
ether extract of the roots and hypocotyls, however, amounts to 1 per cent, 
at the first stage of the seedling and to i-6 per cent, and i-8 per cent, respec- 
tively in the next two stages. The amount of soluble acid rises rapidly 
in the last two stages and composes 16-1 per cent, and 18*5 per cent, of the 
ether extract in Stages V and VI respectively. 
The determination of the soluble acids supplements remarkably well 
the results obtained in the estimation of the total insoluble fatty acids. 
Wherever there is a decrease in the percentage of insoluble fatty acids 
there is an increase in the amount of the soluble acids. 
The Iodine Number . By the iodine number of an oil is meant the 
amount of iodine that the combined and free unsaturated fatty acids of an 
oil will take up expressed in percentage of the weight of the oil. It is 
really a measure of the quantity of unsaturated fatty acids in the oil. Thus, 
if the iodine number of the oil decreases during germination, it is indicative 
of the fact that the unsaturated fatty acids of the oil are becoming saturated, 
probably by the addition of oxygen. 
The iodine numbers of the ether extract and neutral oil of the seed 
are practically identical, being 125-5 an d 124-9 respectively. This value 
holds constant for both the ether extract and neutral oil of the cotyledons 
until Stage IV, when there is a like decrease in the value of the iodine 
number of each. The iodine number for each at this stage is 120. At 
this period of development seven-eighths of the original oil have disappeared 
and 13-8 per cent, of the ether extract remaining is composed of free fatty 
acid. In the last stage of germination, when only 5-3 per cent, of the 
original oil remains in the cotyledons, and one-third of the oily material 
present is composed of free fatty acid, the value of the iodine number for 
both the ether extract and neutral oil is the same and amounts to m-8. 
These results are significant in that they indicate that neither the 
combined nor the free fatty acids of the ether extract of the cotyledons 
show any signs of becoming saturated until a late stage of the seedling, 
and even then the degree of saturation is comparatively slight. It further 
indicates that the combined and free fatty acids of the ether extract are 
equally saturated, and that this is the case even when one-third of the ether 
extract is composed of free acid. 
In my previous work I found that the iodine number of the ether 
extract in Stages IV and V fell to 77-5 and 67-4 respectively. I attribute 
this low result, however, to the oxidation of the oil during the preparation 
of the material. In the preparation of the material for this investigation, 
however, methods were employed, as explained elsewhere, which reduced 
the oxidation of the oil to a minimum. 
