THE COLORS OF NORTHERN FLOWERS. 689 



in size. In Gentiana crinita the yellowisli-white bud is nearly an 

 inch long before the purple coloring appears, and the corolla al- 

 ways remains white at base. A stimulus to the growth of the plant 

 makes itseK apparent in the increased brilliancy of the flowers, as 

 when they are exposed to clear sunlight or are treated with nitrate 

 of soda, and may also be observed in the flushing of tulips, by which 

 they lose their variegated colors when treated with strong manure. 

 On the other hand, a check in nutrition and growth will cause a 

 diminution of the perianth in size, accompanied by retrogression 

 in color. When double red poppies are transplanted the whole 

 plant is dwarfed, while the flowers are much smaller and pure white. 

 This view of the origin of white flowers explains why they are the 

 commonest in Nature, accounts for their being most numerous in 

 families in which yellow flowers are likewise numerous, and why 

 they are most true to name under cultivation. Many white flowers 

 also exhibit other evidences of degeneration in their structure. 

 IS^umerous species of Cruciferce and Caryophyllacece have small 

 white flowers, which regularly fertilize themselves; and in Lepidi- 

 um, Stellaria, and Sagina the petals are sometimes present and in 

 other instances are wanting. 



White flowers often develop red or blue coloration. It is in- 

 teresting to note that the red and white varieties of the hyacinth 

 were derived from the wild blue form earlier than the yellow. 

 Darwin gives an instance of a white and red rose produced on 

 the same root, also of white and pink flowers on a single plant of 

 Antirrhinum ma jus. Cratcegus oxyacantha, a dark pink hawthorn, 

 has been known to throw out a tuft of pure white blossoms. Every 

 stage of the transition from white to red is placed before us by the 

 rose family. The thorns are white, rarely tinged with rose ; in the 

 pear and apple the flowers are white, regularly shaded with red; 

 and one of the Spirceas is rose, rarely white, while in the roses 

 proper the six species are rose-colored, but the prairie rose changes 

 to white. Under cultivation the wild geranium has been seen to 

 produce upon the same plant both white and blue flowers. Good 

 examples of the transition from white to blue and from blue to 

 white may be met with in the Eanunculacew and Leguminosce. 

 Delphinium tricorne is bright blue, sometimes white, Viola cana- 

 densis has the petals white inside but the upper ones tinged with 

 violet beneath, Astragalus has a part of the species white and a part 

 purple, while it is common to find blue and white varieties of He- 

 patica growing on the same grassy bank. White flowers pass more 

 readily into red, blue, or yellow than any one of these colors can be 

 converted into any other, since it is easier to develop a new pigment 

 than to transform one already existing. This is confirmed by the 



VOL. LV. 48 



