HE casual observer may perhaps 
have noticed that interesting law 
of nature which governs the color- 
ing of flowers, and which confines 
the hues of a given flower, or per- 
haps a botanical group of flowers, 
to two colors and the combination of these col- 
ors. The three primary colors red, yellow, and 
blue are rarely to be seen in the blossoms of the 
same botanical group. Thus we observe roses, 
hollyhocks, chrysanthemums, and tulips in all 
shades of white, yellow, pink, red, and crimson, 
even almost approaching black, and numberless 
combinations of these colors, but never blue. The 
same is true with dahlias, zinnias, lilies, gladioli, 
pinks, and portulacas. 
On the other hand, flowers which are notably 
blue as in the bell worts, or " Canterbury -bells," 
