72 



NORMAL AND EXPERIMENTAL POLLINATION. 



A second corolla slipped over the staminode. — This gives the flower 

 an unusual appearance, as though it were doubled, and interferes with 

 entrance to the corolla. Osmia melanotricha and 0. pentstemonis landed 

 and tried to enter, but failed. 



Comparative relations. — An experiment in which normal, mutilated, 

 and inverted flowers were placed in the same group was devised to determine 

 the effect of competition. Three spikes of each type of mutilation and an 

 inverted one were used with 11 normal spikes for comparison. Table 51 

 shows the results. 



Table 51. — Inverted and mutilated flowers. 



ARTIFICIAL AND PAINTED FLOWERS. 



The flowers of this species are bright blue in color and stand out conspic- 

 uously against the buff of the gravel-slides on which they grow. The 

 racemes are 6 to 12 inches long and each plant has several, so that the color 

 mass is large and conspicuous from some distance. 



Crepe-paper corollas. — The corollas of half the flowers of 4 racemes (25 

 flowers) were removed and replaced by tubular paper corollas in red, blue, 

 green, white, or yellow. Although the normal flowers were visited as usual 

 during the morning, no insects even attempted to enter the artificial ones. 



Corolla painted with water-colors. — Half of the flowers on 5 racemes 

 were painted red, yellow, or green. One Vespa germanica passed by red and 

 yellow to work on the normal ones adjacent. Another Vespa observed 

 went to 2 flowers painted yellow, but passed by the neighboring red ones. 

 Clisodon terminalis entered the normal flowers, but ignored the painted ones. 

 Osmia pentstemonis was less discriminating and different individuals visited 

 the yellow flowers repeatedly. They flew from yellow to normal flowers 

 and then to red ones, etc., as they found the flowers in a convenient order, 

 but they avoided the green ones to some extent. One individual inspected 

 the green, but passed to work at yellow and red, and then returned to the 

 green. It next went to yellow, to red, to a normal flower, and then back to 

 red. 



HONEY AND ODOR. 



Sirup added. — Diluted Karo sirup was placed in various positions on the 

 flower. One individual of Osmia pentstemonis entered blossoms with a drop 



