blessed thistle: annual of Mediterranean to Portugal having hairy stems and minutely spiny-toothed leaves and large heads of yellow flowers
thistle: any of numerous plants of the family Compositae and especially of the genera Carduus and Cirsium and Onopordum having prickly-edged leaves
vincristine: periwinkle plant derivative used as an antineoplastic drug (trade name Oncovin); used to treat cancer of the lymphatic system