Robertson — Flowers and Insects. 171 



usually effect cross-pollination. Spontaneous self-pollination 

 may occur by the pollen falling upon the stigma. According 

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

 onogamy results from the stamens diverging so far that the 

 pollen may fall upou the stigmas of surrounding flowers. 



According to Kirchner (9), V. lanlana 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 mm. 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 — Dermestidae : (1) Antbremus musaeorum L., freq., (2) Cryp- 

 torhopalum triste Lee; (3) Orpbilus glabratus F., ab.; Scarabaeidae : (4) 



