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To elucidate the classification and relationships of the Korean Ulmaceae, the morphological characters of 13 species and two varieties belonging to five genera were examined. Ulmus is distinguished from other genera by the presence of bisexual flowers, compound teeth, epipetalous stamens, flower buds, and determinate inflorescences. Aphananthe possesses craspedodromous venation with distinct third venation, suggesting that this genus seems to bridge the morphological gap between the Ulmoideae with craspedodromous venation and the Celtidoideae with brochidodromous one. This finding, therefore, does not support the familial position of both subfamilies. Both Ulmoideae (Ulmus with bisexual, Hemiptelea with polygamous, Zelkova with unisexual flowers) and Celtidoideae (Celtis with polygamous, Aphananthe with unisexual flowers) tend to develop unisexual flowers. Characteristics of the lobed perianths and straight stamens in Ulmoideae and the parted perianths and curved stamens in Celtidoideae suggest to be correlated with the trends from insect pollination to wind pollination. Ulmoideae having lens-shaped ovaries and samara fruits is distinguished from Celtidoideae having tubular ovaries and drupe fruits. However, Zelkova has the flat -reniform nuts, showing the intermediate state of the two. Also, bract type and anther orientation support the separation of the family into two subfamilies. |
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