A study of histogenesis of integuments in Euphorbiaceae using phase contrast, and an pplicatin of its utility to embryology.

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Using phase contrast and Nomarski interference optics, the histogenetic origin of integuments in Euphorbiaceae that has been reported to be unusual in angiosperms in reinvestigated, and the utility of those new approaches is examined in observing embryological features of Celtidaceae and Ulamceae.1. The inner integument of Euhorbiaceae, based on observations in Acalypha australis, Euphorbia helioscopia, E. supina, and Phyllanthus urinaria, is found to be of dermal origin, rather than is it of subdermal origin as reported earlier (Bor & Bouman, 1974; Bor & Kapil, 1976). Nomarski interference optics clearly distinguish cell derivatives in developing integuments. This result concludes that there is no longer a gap in histogenetic pattern of integument between Euphorbiaceae and other angiosperms.2. An extensive observation on pollen cell number in Geltidaceae-Ulmaceae (comprising 15(-18) genera) is made for the first time. Two-celled pollen is found to occur in Aphananthe aspera, Chaetacme aristate (Celtidaceae), Holo-ptelea integrifolia and Hemiptelea davidii (Ulmaceae); both 2- and 3-celled pollen in Planera aquatica and Zelkova serrata (Ulmaceae); 3-celled pollen in Ulmus davidiana. The results suggest that an evolutionary change from 2- to 3- celled pollen has occurred in a restricted group of several genera in Ulmaceae but not in Celtidaceae.3. Based on observation of young ovules of Aphananthe aspera, it is found that Nomarski interference optics easily demonstrate some embryological features such as the bitemy, crassinucellate condition, etc.