THE PROBLEM OF SELECTING UNIFORM SAMPLES OF LEAVES

Abstract

The uniformity in composition of samples of leaves of Bryophyllum calycinum was tested by statistical analysis of the data obtained in duplicate for solids, ash, N, protein, and starch. Three sets of 5 samples each were collected, one by a method, referred to as the statistical method, which balances equally among the samples the effects of differences among plants, leaf positions, and leaflet positions; a 2d set by a modification of the opposite leaf method; and a 3d by a method of randomization according to leaf size. Comparison of the results of the duplicate detns. showed that the several analytical procedures were of unequal reliability, that for ash being the least precise. After segregation of the analytical error, the net variation among samples was detd. for each method of collection and for each constituent. The 5 constituents showed no differences in variability and the statistical method gave the most uniform samples. To obtain by either of the other 2 methods the same precision as was secured by the statistical method, approx. 4-5 times as many samples would be needed.