Glycine tomentella, a perennial soybean suspected of outcrossing, was investigated for floral characters that differ from annual cultivars (cvs) of Glycine max, Clark, Wells, and Beeson, that do not outcross readily; and for floral characters that are similar to cv Raiden, an annual very attractive to pollinators. Characters compared include flower number, arrangement, and days opened, and nectary structure and starch accumulation. The nectaries of the perennial and annuals were examined and compared with each other at the following stages: 2 days before anthesis, 1 day before anthesis, anthesis before the petals open, anthesis after the petals open, 2 days after anthesis, and 3 days after anthesis. In the perennial and the annual cvs, starch is present in all cell types of the nectary, but is particularly concentrated in the cells to the outside of the phloem fingers. There appears to be a trend of greater starch accumulation one day before anthesis within nectary cells of G. tomentella and G. max cv Raiden than occurs in the other cvs of G. max. In all of them, the starch is noticeably less just prior to flower opening, and almost gone after flower opening, the time during which nectar is secreted. In the annual cvs all but a few guard cells lose their cellular contents, and the nectaries collapse. The processes of starch degradation and nectary collapse occur within a 24 hr period. In the perennial, a zone of special parenchyma cells surrounding the phloem fingers becomes completely vacuolated, and collapses. However, the epidermal and subepidermal cells in a zone 3-10 cells deep remain cytoplasmic even after the flower has withered, so that the nectary does not fully collapse until floral excision or early pod development. Implications of these observed differences will be presented with respect to pollinator insect attraction.