appearances attracted attraction carnivorous carnivorous-plants clumps clusters coloring colors colouring colours cover digest digested digesting display edge edges enzymes flora funnel herbaceous insect-trap insects nectar-like-secretions nutrient-source nutrients operculum perennials pitcher pitcher-plant plant prey proteases rim sarracenia species trap unusual variations variety various vegetation botanic garden botanics catch danger devour digests eating flies flower flowers fly Flytrap glasgow green grip insect insect eating nature nutrition pitcher plant plants purple red sarracenia purpurea savage attract-prey carnivore distinctive passive-trap pitcher-plants pitchers pitfall-traps rims slippery veins