THE FLOWER AND THE BEE 



in the floral world, and undoubtedly blue flowers, as a whole, 

 were the latest evolved. They adorn the culminations in flower- 

 building. Simple, small, regular flowers, as has already been 

 shown, are usually white or yellow, as the water-plantains, 

 buttercups, and fivefingers, while many red flowers are also 

 primitive in structure. But corollas which are two-lipped, or 

 bilaterally symmetrical, and highly modified are most frequently 

 blue or blue-purple and are often variegated with other hues. 

 For instance, in the buttercup family, while the buttercups are 

 yellow, the bilateral larkspurs and monk's-hoods have blue 

 sepals and petals. Again, in the rose family the regular rotate 

 fivefingers are yellow and the roses are white or red, and blue 

 flowers are entirely absent; but in the "sister family" of the 

 pea family (Papiliojiacece), where the corolla is butterfly- 

 shaped, blue and blue-purple forms prevail, which are polli- 

 nated by bees. (Figs. 20, 36, and 37.) 



In blue flowers the cell-sap is neutral or alkaline, and the 

 anthocyanin salts are violet-colored or various shades of blue 

 and purple. There may be only a single pigment or a mixture 

 of pigments. The color change from red to blue may be arti- 

 ficially illustrated by dipping a red rose in an alkaline solution, 

 when it becomes blue, but the red hue is again restored by an 

 acid. Many individual flowers illustrate this color transition. 

 The flowers of the common borage (Borago officinalis) are at 

 first red, but later turn blue, as do those of the lungwort 

 (Pulmonaria); the corolla of the stickseed is red before ex- 

 panding, but afterward becomes bright blue, and the pale-pink 

 blossoms of the forget-me-not also soon change to blue. The 

 gradual transition from an acid cell-sap to an alkaline one is 

 shown by fruits, which are at first sour and red, but with ma- 

 turity become sweet and blue or purple. The reverse change 

 of color may also take place, and in a variety of perennial phlox 



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