Page:An introduction to physiological and systematical botany (1st edition).djvu/338

 l308 teeth, as in Tragopogon, t. 434, and the Dandelion; or tubulosi, tubular, cylindrical and 5-cleft, as in Carduus, t. 107, and Tanacetum, t. 1229. The marginal white florets of the Daisy are of the former description, and compose its radius, or rays, and its yellow central ones come under the latter denomination, constituting its discus, or disk. The disk of such flowers is most frequently yellow, the rays yellow, white, red, or blue. No instance is known of yellow rays with a white, red, or blue disk.

An Aggregate flower has a common undivided Receptacle, the Anthers all separate and distant, Jasione only, ''Engl. Bot. t.'' 882, having them united at the base, but not into a cylinder, and the florets commonly stand on stalks, each having a single or double partial calyx. Such flowers have rarely any inclination to yellow, but are blue, purple, or white. Instances are found in Scabiosa, t. 659 and 1311, Dipsacus, t. 1032 and 877, and the beautiful Cape genus Protea.

Such is the true idea of an Aggregate flower, but Linnæus enumerates, under that