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The xylem strands observed in 15 species of the Malaysian Athyriaceae appear to provide useful characters for distinguishing between the genera. Alhyrium and Diplazium show a similar type of xylem strand: they possess two xylem strands in their stipe. In contrast, the stipe of Deparia shows five xylem strands at the base of the stipe. The two types of xylem strand seems to support the taxonomic segregation of the genera. In Aspleniaceae, all 12 Asplenium species studied are similar: they have binary xylem strands in the stipe which unite in the rachis to form a single X-shaped strand.
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Y. Umikalsom (1992) studied this question.
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