Bot. [L. calcar, calcāri- spur, f. calc- heel + -āri- belonging to: see -AR.]
A hollow ‘spur’ from the base of a petal.
1836. Penny Cycl., VI. 138/2. Calcar, or spur in flowers, is a hollow projection from the base of a petal, and has usually a conical figure.
1880. Gray, Bot. Text-bk., 400. Calcar. A spur; mostly used for the nectariferous one of a calyx or corolla.
