The interrelationship between oil content and various other characters such as ripening period, refractive index, iodine value, seed size etc. were determined from observations recorded on one hundred varieties of linseed from the genetic stocks being maintained at the Indian Agricultural Research Institute, New Delhi. The effect of grouping the varieties, on the basis of seed colour and seed size, on the correlation coefficients obtained between the different characters, pertaining to oil content and quality was studied. Out of ten total correlation coefficients considered in two cases only i.e., (1) between oil content and refractive index and (2) between refractive index and seed size, there was evidence for the heterogeneity of the different estimates of ‘ r ‘. Among the nine partial correlations worked out in one case only i.e., between oil content and iodine value eliminating seed size, was the estimates of ‘ r’ found to be significantly affected as a result of the grouping. Thus in all, in about fifteen per cent of the cases considered there was definite indication that grouping of the varieties materially affects the trend and the value of the correlation coefficient. This strengthens the need for caution in extrapolating from the correlation existing in one artificial group to another group of varieties.
