286 NEW YORK STATE MUSEUM 



function of a calyx for the entire flower head. The individual bracts are 

 often leaflike in character. 



Two kinds of flowers are to be noted in the " heads " of certain 

 Compositae. They are the regular five-toothed or five-lobed corolla, as 

 seen in the different species of Eupatorium, and the irregular, strap-shaped 

 or ligulate corolla, in the ray flowers of the Wild Asters. Sometimes both 

 kinds are fovmd in the sanie head, as in the common Daisy, and then the 

 strap-shaped flowers around the margin are referred to as ray flowers, and 

 the densely packed tubular flowers in the center of the head are called 

 disk flowers. Very often the disk fiowers are of one color and the ray 

 flowers of a difi^erent color. In some cases we find heads composed entirely 

 of disk flowers (Thistles). 



The stamens are five in number, attached to the inside of the corolla 

 tube and usually cohere by their anthers in a ring around the style, which 

 is commonly two-cleft at the summit, that is, a two-parted stigma. The 

 ray flowers are usually without stamens, when disk flowers are present, 

 and sometimes some flowers (either disk or ray, as the case may be) are 

 entirely neutral (without stamens or pistils). The ovary is one-celled, 

 containing one ovule which ripens into a small, dry, one-celled, one-seeded, 

 indehiscent fruit, known as an achene. This achene is admirably adapted 

 for seed dissemination by means of the persistent pappus, which matvires 

 along with the fruit. In the case of Bidens, the pappus consists of two 

 barbed processes projecting from the achene, which catch in the shaggy 

 coats of animals and on the clothing of passing persons and is thus dis- 

 tributed wide distances. In other cases the pappus consists of hairlike 

 tufts, as in the Thistle, which enable the seed to be carried great distances 

 by the wind. 



The Compositae represent the most highly developed family of flow- 

 ering plants, in respect to floral structure. By massing the flowers in 

 heads, there is a great economy of space and tissue gained for the plant, 

 and also greater certainty of pollination for the individual flowers, as a 

 visit from one insect may result in the pollination of from several to many 



