The umbel-like peduncles are situated in the axils of the leaves or spring from the nodes of leafless branches.    From Wordnik.com.  [Scientific American Supplement, No. 288, July 9, 1881] Reference

Sterile and fertile flowers on the same tree, appearing when the leaves are fully grown, -- sterile at the base of the season's shoots, in slender, pendulous, downy catkins, 4-8 inches long, usually in threes, branching umbel-like from a common peduncle; scales.    From Wordnik.com.  [Handbook of the Trees of New England] Reference

Sterile and fertile flowers on the same tree, appearing when the leaves are fully grown, -- sterile at the base of the season's shoots, in pendulous, downy, slender catkins, 3-5 inches long, usually in threes, branching umbel-like from a common peduncle; scales.    From Wordnik.com.  [Handbook of the Trees of New England] Reference

Sterile and fertile flowers on the same tree, appearing when the leaves are fully grown, -- sterile at the base of the season's shoots, or sometimes from the lateral buds of the preceding season, in slender, pendulous catkins, 3-4 inches long, usually in threes, branching umbel-like from a common peduncle; scale 3-lobed, hairy-glandular, middle lobe about the same length as the other two but narrower, considerably longer toward the end of the catkin; stamens mostly 5, anthers bearded at the tip: fertile flowers on peduncles at the end of the season's shoots; calyx 4-lobed, pubescent, adherent to the ovary; corolla none; stigmas 2.    From Wordnik.com.  [Handbook of the Trees of New England] Reference