32 



NORMAL AND EXPERIMENTAL POLLINATION. 



this was less than one-eighth of the number paid to natural ones at the same 

 time. All the colors received visits, as follows : red 3, yellow 22, green 3, 

 blue 17, white 4. In accordance with the general rule, painted flowers 

 were visited much more than paper ones, doubtless owing to the fact that 

 they differed but little from the normal ones, as shown especially by the 

 behavior of Bombus. The attractive power of honey was again found to be 

 slight, flowers with honey receiving but one visit to 4 for the normal ones. 



RUBUS STRIGOSUS. 

 NORMAL POLLINATION. 

 Habit and structure. — These flowers open later than those of Rubus 

 deliciosus, but the two are in bloom together for a considerable period. 

 They are quite inconspicuous because of their small size and recurved 

 petals and the scattered position among the leaves. However, the large 

 amount of easily available nectar makes this species very attractive to 

 several kinds of insects. The nectar is formed within the stamen circle 

 at the base of the ovaries. It oozes out in drops and if not kept lapped up 

 by the bees, the depressed ring becomes filled with it. In order to find out 

 how rapid this flow of nectar is, 4 plants profuse with flowers were covered 

 with paper bags in the evening, so that no visitors could get nectar until 

 the flowers were examined. At 9 the next morning, when the visits of the 

 bees were becoming numerous, the bags were removed. Flowers outside 

 the bag, which had been receiving the morning visitors, showed only the 

 glistening droplets of nectar, while a full nectar ring was very conspicuous 

 in all the bagged flowers mature enough to produce it (plate 3). 



Behavior. — A pis mellifica hangs suspended from the flowers while 

 sucking nectar. It scrapes pollen from its head and thorax with the 

 second pair of legs on to the corbiculse of the third pair. One individual 

 flew half an inch above flowers with dry anthers and discovered without 

 landing that there was no nectar. Prosopis episcopalis goes to open flowers 

 for nectar and lands on the petals. If the petals are closed, it goes around 

 the edge of the bud and inserts its ligule between the petals. The normal 

 visitors on 3 successive days during periods of 2 hours to 100 open flowers 

 are listed in table 13. 



Table 13. — Visitors on three successive days. 



Rubus strigosus is primarily a honey-bee flower, as is shown by the fact 

 that 199 of the 279 visits were made by Apis; of the remaining 80 visits, 

 61 were made by Bombus. 



