Robertson — Flowers and Insects. 171 



usually effect cross-pollination. Spontaneous self-pollination 

 may occur by the pollen falling upon the stigma. According 

 to Keruer (13), the flowers have an aminoid scent, and goit- 

 onogamy results from the stamens diverging so far that the 

 pollen may fall upon the stigmas of surrounding flowers. 



According to Kirchner (9), V.lantana resembles V.opulus, 

 and spontaneous self-pollination may cocur in the same way. 

 Schulz (12) finds it proterogynous with long-lived stigmas. 

 Spontaneous self-pollination is not the rule and is superfluous 

 on account of the visits of numerous insects which may effect 

 self- or cross-pollination. Kerner (13) observes a similar 

 scent to that of V. opulus and the occurrence of geitonogamy 

 in this species. 



Viburnum pubescens Pursh. — According to Patterson's 

 Catalogue, this plant has been found by Bebb, in Winnebago 

 County, and by Vasey, in McHenry. A few plants occur 

 here, on a high creek bank where it was first found by 

 Andrews. 



The white flowers are arranged in nearly flat-topped co- 

 rymbs, which measure about 3 cm. across. The corolla forms 

 a shallow bell about 2 mm. deep, the lobes expanding about 

 7 mm. Nectar is secreted by the conical base of the style, 

 and seems to be quite abundant. 



The flowers are homogamous. The stamens rise from 4 to 

 5 ram. above the stigma and are often so divergent that geit- 

 onogamy may occur by the pollen falling upon the neighbor- 

 ing stigmas. Spontaneous self-pollination may be effected in 

 a similar way by the pollen falling upon the stigma of the 

 same flower. Cross-pollination must often result from the 

 abundant insect visits. 



The flowers bloom from May 6th to 25th. Most of the 

 shallow flowers blooming at the same time show a preponder- 

 ance of the less specialized bees — Andrenidae — and flies. 

 The preponderance of beetles in this case seems to be no kind 

 of an accident. The following insects were taken on the 

 flowers on May 9th : — 



Coleoptera — Deiinestidae : (1) Anthremus musaeorurn L., freq., (2) Cryp- 

 torhopalum triste Lee; (3) OrpMlus glabratus F., ab.; Scardbaeidae : (4) 



