Two types of force gauges were utilized to provide accurate measurements of the ability of cottonseed to withstand force applied at a right angle to the long axis of the seed. These measurements were designed to simulate the actual type of damage which the seeds might sustain during harvesting and conditioning operations.

A manually operated Dillon force gauge, calibrated in Newtons, as well as an automatically actuated VanKel, Inc. pharmaceutical tablet hardness testing instrument were utilized in these studies. Measurements of seed coat thickness, as well as the cellular morphology of the cell layers making up the seed coat were made using the scanning electron microscope. Because, as would be expected, the physical characteristics of the seed coats of individual seeds drawn from any specific lot varied, populations of seeds were analyzed, the results were statistically evaluated, and characterized graphically.

In many cases, the structure of the palisade cell layer of the seed coat could be associated with the relative ability of that seed source to withstand cracking damage. The palisade cell layer thus has shock absorbing properties of benefit to seed when it is roughly handled. Distinct differences in the amount of force necessary to cause the seed coat to crack could be observed between seed of diverse genetic backgrounds. Average force necessary to cause the seedcoat to crack ranged from about 60 to 150 Newtons, with low moisture seed. Both "fuzzy" and delinted seeds can be evaluated. The proportion of already damaged or immature seed can be readily calculated as they break at significantly less force than sound seed of the same genetic background.

Significant differences in seed coat strength were observed in tests of populations of seed produced at various locations and in successive years; however, these differences were normally less marked than those seen between a number of genetic strains of both upland and pima cotton. Work in progress is designed to evaluate the possible relation between seedcoat structure and strength, and the susceptibility of the seed to produce fragments during ginning.