COMPOSITAE COMPOSITE FAMILY 
This is the largest family of flowering plants, likewise the 
highest as it ranks above all others in complexity of structure 
and physiological processes, in relationship to insects and in 
method of seed dispersal. Some of its members are pernicious 
weeds, many are used as garden and greenhouse flowers, but 
otherwise surprisingly few are of economic importance. 
The individual flowers in this family are small and pro- 
duced in dense clusters called heads. What is commonly 
called a Dandelion flower, for example, is really a head com- 
posed of a large number of individual flowers. In the case of 
the Dandelion all the flowers have flat straplike corollas. Ina 
plant like the Sunflower, on the other hand, the outermost 
flowers of the head, called ray flowers or more commonly rays, 
have strap-shaped corollas; the others, in the center and called 
disk flowers, have tubular corollas. A third type of head, such 
as in the White Snakeroot, has the corollas of all its flowers 
tubular. 
The calyx, always above the ovary, is very much modified 
in these flowers and is called a pappus. In some cases it is 
composed of hairlike bristles and in others of awns or scales, 
and in a few genera it is lacking. The style of the sterile 
flower is always 2-cleft. 
The head is in all cases surrounded by an involucre of more 
or less leaflike bracts. In many species there are bracts or 
scales on the receptacle among the flowers, spoken of as 
chaff. When they are absent the receptacle is said to be naked. 
Cross-pollination is the rule among the Composites. In all 
species described in this book the anthers are grown together 
around the style and the pollen sacs open on the inward side. 
As the flower opens, the style, with its stigmas closed, pushes 
up through the united anthers, scraping pollen from them. 
The pollen mass remains partly adherent to the anthers and 
falls over onto their upper ends, instead of being carried along, 
as the style grows past. Only after the style has grown beyond 
the anthers do the stigmas open to receive the pollen which 
insects will bring from other flowers. 
It will often require close observation to distinguish the 
different kinds of Composites but there should not be much 
_ difficulty in recognizing the ones included in this book. Many 
_ not included here are likely to be found, however, and for them 
_ more comprehensive manuals should be used. 
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