Traditionally, all varieties of cannabis are derived from sativa, over the years they have been breed out and are now a combination of sativa and indica, depending on the breeder.
However, there is a third sub-species of cannabis known as ruderalis. Cannabis ruderalis, differs from sativa and indica varieties it two significant ways. Firstly, it contains little if any THC, and secondly, ruderalis plants reach maturity (i.e. flower) a set time after germination – flowering is not induced by changes in the light period.