NATURAL PHILOSOPHY. 195 



might have been inferred that order prevails also in the distribution of 

 colors. This is not only the fact ; there are, besides, obvious indications 

 of a relation between the color and form of certain organs. 



The presence of all the colors, red, yellow and blue, which form com- 

 pound or white light, is a physical want of the organ of vision. Among 

 the lower tribes of plant?, the algee maybe mentioned as remarkable exam- 

 ples of constantly associated colors. Such in fact is Prof. Harvey's classi- 

 fication, who divides them into red, green and olive. Among the red 

 there are many which have a red- purple hue ; and among the olive, not a 

 few are yellow-green. lied and green are complementary, and red-purple 

 and yellow- green stand in the same relation. Among mosses, we find the 

 red or red-purple peristome associated with the green or yellow-green 

 capsule, and the same is true of their stems or leaves. In flowering plants, 

 the associations of certain colors are so numerous that it is unnecessary in 

 this summary to do more than mention a few examples. In the leaves of 

 Caladiam pictum, Coleus Blumei, and Victoria Hegia, we find red or red- 

 purple associated with green or yellow- green. The same is true of the 

 pitcher-like organs of Sarraceniie, Nepenthes, and Dischidia. In the 

 flower, similar associations of various kinds are common. "SVe need not 

 expect to find in a corolla or any other organ the primaries, red and yellow, 

 or blue and red, associated and in contact. The red has green, the yellow, 

 has purple, and the blue has orange associated. Of the primaries, blue is 

 rarest, many cases so denominated being, in fact, red-purples. In the 

 flower yellow predominates ; hence the very general diffusion of purple of 

 various degrees of intensity. Purple being of such general occurrence in 

 the flower, we can now understand why yellow is the most common color 

 of pollen : some exceptional cases seem to confirm this ; in the turn- cap 

 lilly, for example, the red pollen is associated with the green filaments. 

 The color of the flower may have its complement in that of other parts, as 

 the stem, leaf, &c. Sometimes the associated colors are not visible at the 

 same time. The inside of a ripe fig is red-purple, the outside yellow- green. 

 Sometimes a yellow corolla is succeeded by a purple fruit. Direct expo- 

 sure to light, although usually and in general correctly admitted to have a 

 Qlirect relation to intensity of color in organisms, appears not to be neces- 

 sary in every instance. The plant, however, must receive the light at 

 some part or other, in order to produce that intensity of color observed in 

 the coats of seeds, in the interior of fruits, and in the tissues of subterra- 

 nean organs. In conclusion 1. The primaries, red, yellow and blue, 

 are generally to be seen in some part of the plant. 2. When a primary 

 occurs in any part of the plant, its complement will usually be found in 

 some other part, or at some period or other of the development of the 

 plant. I have found in not a few instances, in the animal kingdom, simi- 

 lar associations of color ; birds, niollusca and radiata present many obvi- 

 ous examples. AVe may next examine the relation between color and 

 form ; and the remarks are, for the present, confined to the flower. Law 

 1. In regular polypetalous and gamopetalous corollee jthe color is uniformly 



