JULY 15, 1912 



437 



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THE PURPLE AND BLUE FLOWERS OF NORTH 

 AMERICA 



Do Bees Show Preference for any Color ? Are 

 they Color Blind ? 



BY JOHK H. LOVELL. 



There are 422 purple flowers in our east- 

 ern flora. Purple is an artificial rather than 

 a natural categoiy, and the term is used 

 rather as a matter of convenience. It is 

 widely used by systematic botanists, and, 

 though open to many objections, there 

 seems to be no convenient substitute avail- 

 able. If an accurate scale of colors should 

 ever be adopted it will very likely be dis- 

 carded altogether. All colors with their 

 various tints and shades, including the 

 browns and grays, are represented in the 

 solar spectrum except purple. This sensa- 

 tion is produced by the combination of two 

 sets of light-waves — -red and blue, or violet. 

 Often purple flowers contain two or even 

 three pigments. It has been suggested that, 

 instead of attempting to name their hues, 

 the percentages of the different colors com- 

 posing them should be given. By using 

 Maxwell's color-wheel the purple of the 

 dahlia may be produced by mixing 14 per 

 cent red, 7 per cent blue, and 79 per cent 

 black. Heliotrope purple is produced by 

 mixing 25 per cent each of red, blue, black, 

 and white. Wbile such formulae have the 

 value of accuracy, it may well be doubted 

 whether they would convey to the average 

 person much idea of the color of the flower. 



Purple flowers may be divided into three 

 groups — dull or lurid purple, red purple, 

 and blue purple. Red purple should usual- 

 ly be classed with red flowers, wliieh as a 

 rule they resemble in structure and manner 

 of pollination, as in the orchis, geranium, 

 loosestrife, and evening-primrose families. 

 On the other hand, blue-purple flowers be- 

 long with blue flowers, as in the pea, fig- 

 wort, and mint families. 



Dull or lurid purple flowers are often 

 adapted to flies. The purple trillium, which 

 children so often gather in early spring, 

 only to throw away soon because of its dis- 

 agreeable odor, contains no nectar, and is 

 attractive to flies alone. In the lurid-pur- 

 ple flowers of the Dutchman's pipe, the 

 calyx is prolonged into a tube, with a con- 

 tracted throat, either straight or shaped 

 like the letter S, which is set inside with re- 

 flexed hairs. Flies can creep in easily, but 

 the hairs prevent their escape. As soon as 

 the anthers have ri] ened, the hairs wither, 

 and the imprisoned insects, now more or 



less covered with pollen, are set free. These 

 flowers should be compared with the pitch- 

 er-Hke leaves of the pitcher-plant and the 

 spathes of Jack-in-the-pulpit, as all three 

 serve as tr&ps for small flies, and are lurid 

 purple, a color which is thought by some to 

 be attractive to these insects. 



Brown flowers usually owe their hues to 

 a mixture of chlorophyll or carotin with 

 anthocyan. There are two kinds of pig- 

 ments in the flowers of the Carolina allspice 

 and the North American papaw, in goose- 

 berries, and various species of orchids. In 

 the European flora, bartsia has black flow- 

 ers; but I know of no wild flowers in the 

 Eastern States which are black, though a 

 number have black centers; but under cul- 

 tivation we have black pansies and tulips. 



. .THE BLUE PLOVPERS OP NORTH AMERICA. 



The blue flowers in northeastern America 

 number 325. Blue is the highest color in 

 the floral world, and undoubtedly blue flow- 

 ers were the last to be evolved. Blue is 

 Nature's favorite color, the hue which she 

 has reserved to adorn her culminations in 

 flower-building. Simple, small, regular 

 flowers, as has already been shown are usu- 

 ally white or yellow, as the water-plan- 

 tains, buttercups, and five-fingers; but gen- 

 era and families with highly modified odd- 

 shaped corollas are most frequently blue- 

 purple or blue, and often they are varie- 

 gated with other hues. For instance, in the 

 buttercup family, while the buttercups are 

 yellow the bilateral larkspurs and aconites 

 have blue sepals and petals. Again, in the 

 rose family the regular rotate five-fingers 

 are yellow and the roses are white or red, 

 but there are no blue blossoms; but in "the 

 sister family" of the Papilionaceae or pea 

 family, where the corolla is butterfly-shap- 

 ed, blue and blue-purple forms are com- 

 mon. 



Many violets are also blue, but some spe- 

 cies occasionally revert to yellow. In some 

 flowers of viola tricolor the petals are yel- 

 low when they open, and gradually change 

 to blue, wliile others change to blue before 

 they open. There are varieties of the pansy 

 with both yellow and blue flowers, and a 

 number of the simpler sjDeeies of this genus 

 always have yellow flowers. Thus there is 

 good reason for believing that the primitive 

 or ancestral forms of the violet family were 

 yellow. All the twelve species of the spi- 

 derwort family, except one which is rose- 

 colored, have blue flowers. They are at- 

 tractive to bees, as are also many blue flow- 

 ers in the lily and iris families. 



