This text reports the tracks of studying to the shape and density of gland trichomes for 11 different genotype of flue﹣cured tobacco in mature period.

The main circuits of a magnetic head positioning system with a density of 8 tracks per millimeter (TPM) based on a 4 TPM system are described with the performance of the system analysed and discussed.

In addition to the density of fission tracks (apparent age), the change of their length and distribution can provide the information of paleotemperature.