CHAMAENERIUM ANGUST1F0LIUM. 45 



SUMMARY. 



Complete inversion of the flower did not deter bees from landing, but 

 it did prevent their finding the nectaries. As a rule, they also alighted on 

 flowers with the nectaries concealed by cotton, but Bombus alone succeeded 

 in finding the nectar. The total number of visitors to the mutilated flowers 

 was twice as great as the normal. This was due chiefly to the greater 

 attractiveness of the flowers with stamens excised, since the removal of 

 the petals almost completely destroyed the attraction and shortening 

 them greatly reduced it. Paper flowers received a considerable number 

 of visitors, but they were only about a tenth as attractive as the normal 

 ones. The effect of honey on the flowers was to reduce the number of 

 visitors a half and the number of visits six times. 



CHAMAENERIUM ANGUSTIFOLIUM. 

 NORMAL POLLINATION. 



Habit and structure. — These plants were present in the open spaces 

 along Ruxton and Jack Brooks, where the communities are often so dense 

 and extensive that they practically crowd out all other species where 

 they exist. The blooming period is continuous from the beginning of July 

 until the first of September, the lower flowers on the stalk maturing first, 

 and then as the stalk elongates, the flowers above come into bloom. The 

 long period of blooming and the numerous flowers that mature at any one 

 time make this an admirable plant for study. The great number of visitors 

 always present on bright days indicates that the bees find it a very desirable 

 species. Nectar is abundant and there is a large amount of pollen. The 

 pollen grains are large and of a blue-green color, and are held together by 

 the sticky threads characteristic of the Onagraceae. 



The corollas of the flowers lie in a more or less vertical plane with the 

 style recurved and its branches held closely together, protecting the stig- 

 matic surfaces, or in the later stage with the style projecting in front of the 

 corolla and the stigmatic surfaces exposed on the outwardly coiled stylar 

 branches. The stigmas are covered with blue-green pollen soon after they 

 recurve. A large number of seeds develop, indicating that the method of 

 pollination is unusually efficient. The petals of the flowers are about the 

 size of the Bombus workers and so form a very convenient landing- platform 

 for most of the visitors (plate 8). 



Behavior. — Bombus juxtus is by far the most frequent visitor, although 

 other species of Bombus and Apis are abundant. The former comes for nec- 

 tar chiefly, although it usually collects some pollen in the process, while a 

 few individuals collect pollen alone. Juxtus lands on a petal, pushes out 

 its proboscis, and finds nectar at the openings between the bases of the two 

 upper stamens. While sucking nectar, the hind legs move back and forth 

 in such a way that much pollen accumulates in the corbiculae. This motion 

 shakes the whole flower, and pollen from anthers and from the hairs covering 

 the bee's body falls on the recurved stigmatic surfaces. The hairs on the 

 dorsal and ventral sides of Bombus become dusted with pollen. One 

 Bombus juxtus marked with white paint was found to return to the same 

 group of flowers a number of times each hour, as well as day after day. 



