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Monocotyledons are distinguishable from dicotyledons by their subtype P2 sieve-element plastids containing cuneate protein crystals, a synapomorphic character uniformly present from basal groups through Lilioids to Commelinoids. The dicotyledon genera Asarum and Saruma (Aristolochiaceae-Asaroideae) are the only other taxa with cuneate crystals, but their sieve-element plastids include an additional large polygonal crystal, as is typical of many eumagnoliids. New investigations in Melanthiaceae s.l. revealed the same pattern (polygonal plus cuneate crystals) in the sieve-elementplastids of Japonolirion osense (Japonoliriaceae/Petrosaviaceae), of Harperocalfsflava, Pleea tenuifolia, and Tofieldia (all: Tofieldiaceae). In Narthecium ossifragum a large crystal, present in addition to cuneate ones, usually breaks up into several small crystals, whereas in Aletris glabra and Lophiola americana (Nartheciaceae) and in all of the 15 species studied and belonging to Melanthiaceae s.str. only cuneate crysta... |
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