1907.] 
Graenicher, Pollination of Wisconsin Flowers. 
93 
visiting the flowers in a legitimate way. The following insects 
were seen on the flowers : 
A. Hymenoptera. 
Apidae: (i) Apis mellifera L., worker, s. ; (2) Bombus 
virginicus Oliv., female, s. ; (3) 5. americanonim Fabr., female, 
s. ; (4) B. separatiis Cr., female, s. ; (5) B. ternarius, Say., 
female, s. ; Andrenidse : (6) Andrena mihimikccnsis Graen., 
female, s. and c. p.; (7) A. zicina Sm., female, s. and c. p.; (8) 
A. nivalis Sm., female, s. and c. p. ; (9) A. dubia Rob., male, s. ; 
(10) Halictus lerouxii Lep., female, s. ; Vespid?e : (11) Vespa 
germanica Fabr., s. 
B. Diptera. 
Syrphidae: (12) Pipisa femoralis hw. ; (13) Syrphiis amer- 
icanus Wied. all s. or f. p. 
Ribes gracile Aliehx. Slender gooseberry. 
Robertson (8) has made us acquainted with the mode of 
pollination of this species. In the slender, pendulous flower, the 
calyx-lobes are reflexed, and together with the petals, they serve 
as footholds for the visiting bees. The converging stamens are 
rather long, and extend in the flowers of our region about 1 1 mm. 
beyond the calyx-tube. The latter is 3 mm. deep. By pressing 
up against the filaments, the erect petals, which are only 2 mm. 
long, form a tube which practically constitutes an elongation of 
the calyx-tube. In order to reach the nectar at the bottom of the 
flower, the insect must have a proboscis of at least 4 mm. length. 
This is inserted through one of the openings between two fila- 
ments and the top of a petal. In this species, as in the two pre- 
ceding ones, there are numerous hairs at the bottom of the tube. 
In these flowers we are dealing with proterandry. When the 
first anthers dehisce the stigma is still 4 mm. below the anthers 
(above in the pendulous flower), but on account of a gradual 
(8) Chas. Eobertson. Flowers and Insects. IX. Bot. Gaz. XVII, 
pp. 270-271 (1892). 
