Maas has a suplemental grouping for subgenus Costus with tubular flowers, he calls Section II. Ornithophilus (for their likely pollination by hummingbirds). Costus with tubular flowers are marked "Y". Other Costus with spreading labellums are marked "N". Costus in other subgenera are also marked (usually N) for this characteristic. If this characteristic is unknown or variable, it is entered in the GingersRus Plant Database as "U".
EXAMPLE #1 - COSTUS WITH TUBULAR FLOWERS - These are pictures of Costus species with tubular flowers. The labellums are not appreciably spread outwards.
EXAMPLE #2 - COSTUS WITHOUT TUBULAR FLOWERS - These are pictures of Costus species without tubular flowers. The corolla and base of the labellum may be tubular, but the labellums are spreading, and the flowers may form a funnel shape.