138 THE POPULAR SCIENCE MONTHLY. 



appears in two well-marked varieties : one, found in sunny localities, 

 whose petals are dark yellow, with red at the base; and the other, 

 growing by shaded ditches, with petals of light yellow, and no red at 

 the base. The more conspicuous variety attracts insects, and, as the 

 stigma overtops the stamens, the agency of insects is required to secure 

 fertilization. The flowers of the less conspicuous variety are not 

 visited by insects, and, as the stigma does not overtop the stamens, the 

 agency of insects is not required. The flower is self-fertilizing. These 

 two forms graduate into each other, by connecting links which are 

 found on the sunny edges of ditches. 



Here is a very instructive lesson. Greater amounts of sunlight will 

 account for the richer color of one variety ; and the agency of insects, 

 attracted by the color, will account for the change in structure. We 

 see Nature in the act of species-making. Insects, acting mechanically 

 on the delicate organs of a plant, efiect something more than fertiliza- 

 tion. Let us consider this action more carefully. 



Dr. Ogle has observed the manners of the bee in visiting beans and 

 scarlet-runners. These flowers are arranged to secure cross-fertiliza- 

 tion. The honey they offer must be taken by an insect which will 

 enter by the open door of the corolla-tube. But Dr. Ogle observed 

 that while certain bees visit the flower in the legitimate way, and thus 

 carry pollen from anther to stigma, others have a trick of evading their 

 duty by piercing a hole in the calyx-tube, thus securing the nectar by 

 a short cut. An important fact noted in these observations is, that the 

 same bee always visits a flower in the same way. The inference is, 

 that this habit of nipping the calyx is the result of individual experi- 

 ence. As some bees have acquired the habit, and others have not, 

 another inference is that these insects are intelligent, and that they 

 differ from each other in degrees of intelligence. Our final inference is 

 that, if all bees are ever schooled up to this new art, there must come 

 an end to. our beans and scarlet-runners — unless some modification 

 should occur in the structure of their flowers. 



The salvia is constructed as if with special reference to fertilization 

 by bumble-bees. But Mr. Meehan, who first pointed out the correla- 

 tion, never saw a bumble-bee enter the flower. Under his eye the bee 

 always cut the tube of the corolla. But another observer has see?i the 

 bumble-bee enter the flower and effect fertilization. And he has seen 

 it nipping the corolla-tube to secure the honey by a short cut. A7id he 

 has noticed that the smaller bees entered the corolla-tube^ and that those 

 tchich were too large to get into the flower nipped the tube. This is an 

 important observation, and brings us to the very heart of the matter. 

 The salvia with small corolla-tube, not securing fertilization, stands 

 but little chance of surviving. The flower with large tube invites the 

 bee, is fertilized, and ripens seed. "Natural selection" is going on 

 under our very eyes. Now, if, in " the struggle for existence," a larger 

 race of bumble-bees should appear, the salvia must either vary with 



