Fig. 2
From: An intensive study plot to investigate chestnut tree reproduction
Bisexual catkins from a male-sterile tree (astaminate): General view (a) and close-up view (b). Most stamens are aborted and do not protrude from male flowers. Bisexual catkins from male-fertile tree (staminate): General view (c) and close-up view (d). Stamens have long filaments and are clearly visible