titration apparent 1.50 2.08 1.47 2.00 1.39 2.13 1.11 1.87 As may be seen in Table II,[138] the caffein content of coffee varies with the different kinds, a fair average of the caffein content being about 1.5 percent for _C. arabica_, to which class most of our coffees belong. However, aside from these may be mentioned _C. canephora_, which yields 1.97 percent caffein; _C. mauritiana_, which contains 0.07 percent of the alkaloid (less than the average "caffein-free coffee"); and _C. humboltiana_, which contains no caffein, but a bitter principle, cafemarin. Neither do the berries of _C. Gallienii_, _C. Bonnieri_, or _C. Mogeneti_ contain any caffein; and there has also been reported[139] a "Congo coffee" which contained no crystallizable alkaloid whatever. Apparently the variation in caffein content is largely due to the genus of the tree from which the berry comes, but it is also quite probable that the nature of the soil and climatic conditions play an important part. In the light of what has been accomplished in the field of agricultural research, it does not seem improbable that a man of Burbank's ability and foresight could successfully develop a series of coffees possessed of all the cup qualities inherent in those now used, but totally devoid of caffein. Whether this is desirable or not is a question to be considered in an entirely different light from the possibility of its accomplishment. TABLE III--CAFFEIN IN DIFFERENT ROASTS Rio Santos Guatemala Green 1.68% 1.85% 1.82% Cinnamon 1.70 1.72 1.80 Medium 1.66 1.66 1.56 City 1.36 1.66 1.46 The variation in the caffein content of coffee at different intensities of roasting, as shown in Table III[140] is, of course, primarily dependent upon the original content of the green. A considerable portion of the caffein is sublimed off during roasting, thus decreasing the amount in the bean. The higher the roast is carried, the greater the shrinkage; but, as the analyses in the above table show, the loss of caffein proceeds out of proportion to the shrinkage, for the percentage of caffein constantly decreases with the increase in color. If the roast be carried almost to the point of carbonization, as in the case of the "Italian roast," the caffein content will be almost nil. This is not a suitable coffee for one desiring an almost caffein-free drink, for the empyreumatic products produced by this excessive roasting will be more toxic by far than the caffein itself would have been. _Caffein-free Coffee_