“Cannabis” is the Latin, generic epithet identifying all species of an ancient, historically revered "herb bearing seed." As with all genus names, the word ‘Cannabis’ is always properly capitalized.
It is interesting, though disappointing, to note the pervasive departure from proper form exhibited by scientists and journalists who fail to capitalize a genus name. I interpret this as being symptomatic of the widespread suppressive influence, attributable to an irrational social prejudice that consistently clouds professionalism in authorship.