The physical and chemical features of Cannabis plants grown in the United Kingdom of Great Britain and Northern Ireland from seeds of known origin--Part III: Third and fourth generation studies.

Two further generations of Cannabis plants have been grown from seeds produced by earlier generation plants which were raised in the United Kingdom of Great Britain and Northern Ireland in 1980 and 1981. The original seedstocks were from known countries of origin. Although there are exceptions, both the physical and chemical characteristics of the third and fourth generation plants generally resemble those of their parents. The yields of cannabis vary substantially from year to year. The total tetrahydrocannabinol contents also vary, but are comparable with the levels in the original plants. Tetrahydrocannabinolic acid continues to predominate over free tetrahydrocannabinol and is much higher than in the original plants.