Some Observations on the Reproductive Biology of Three Species of Cornus (Cornaceae)

Surprisingly little information is available on their breeding systems, however.Ferguson (1966), in his treatment of the Cornaceae for the Generic Flora of the Southeastern United States, mentioned that pollination in Cornus is probably by insects, including small creeping Coleoptera and some Diptera and Hymenoptera.He also speculated that cross-pollination is promoted by the difference in style and stamen length, but that self-pollination may occur when the stamens spread and touch neighboring flowers.Because no substantiating experimental evidence was available on the nature of the breeding systems in this genus, controlled pollination experiments were performed on three species of Cornus using plants cultivated at the Case Estates of the Arnold Arboretum, Weston, Massachusetts.These species were C.florida L. (flowering dogwood), native to eastern North America and an understory tree in mixed deciduous forests; C. sericea L. (red-osier dogwood), found along the Atlantic and Pacific coasts of North America, and a widespread shrub common on river banks and in wet thickets; and C. mas L. (cornelian cherry), native to central and southern Europe and introduced into the United States before 1800.It is a small understory tree in oak forests in its native habitat (Rehder, 1940;Seymour, 1969). MATERIALS AND METHODSTwo individuals each of Cornus florida (Arnold Arboretum accession nos.272-51 A and 272-5 IB) and C sericea (843-69A and 843-69B) and three of C. mas (422-67, 424-67A, 424-67B), all growing at the Case Estates, were used for experimentation.Records maintained at the Arnold Arboretum (Case Estates Nursery Catalogue, 1981) indicate that plants of the latter two species were raised from seed, while those of C florida were grafts of a small-flowered form received from the Morris Arboretum in Philadelphia; none of them is a horticultural variety.