Sentence:  The staminate <WSD>willow</WSD> catkins , then , provide their visitors with both nectar and pollen ; a marvelous arrangement , for it provides exactly what the bee queens need to make their beebread , a combination of honey and pollen with which the young of all species are fed . 
Meaning of the word marked with <WSD> tags:  any of numerous deciduous trees and shrubs of the genus Salix