By V. A. Krassilov
This article includes a description of the morphological grades and their linking kinds; a dialogue of seed plant evolution; an outline of early angiosperms and their environments; and a n research of morphological developments in separate organs and their implications for angiosperm phylogeny.
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Extra info for Angiosperm Origins: Morphological and Ecological Aspects
T h e beak is ribbed, abaxially pitted, with the suture m a r k e d by a m e dian g r o o v e , gaping in the ripe cupules (Fig. 6). T h e ovules are solitary, filling the Fig. 6. , a proangiosperm from the Late Jurassic of Burya Basin, Far East, Russia: gynoclade bearing paired cupules (right) and split cupules showing a soliltary anatropous ovule and a rugulate beak (after Krassilov, 1975) compared with a supposedly progenitorial Beania gynoclade (left, after Harris, 1964). locule except in the basal portion, inverted, platyspermic.
T h e scope of the g r o u p is not yet finally determined. T h e bennettites and gnetaleans are included on account of their derived forms, such as Baisia that is distinctly cupulate (Krassilov & B u g d a e v a , 1982), or Eoantha having flower-like gynoecial structures (Krassilov, 1986). W h e t h e r the w h o l e orders or the derived forms alone are proangios p e r m o u s , is left an open question at the m o m e n t . T h e Bennettitales were d o m i n a n t in the M e s o z o i c , declining through the Late Cre taceous u p to the eventual extinction at about the Cretaceous/Tertiary boundary.
T h e pollen c o n e s were cycad-like, with scaly s p o r a n g i o p h o r e s . T h e pollen grains w e r e sulcate asaccate, with an alveolar infrastructure. T h e ovulate cones were loose, pendent, with peltate ovuliphores bearing two ovules. In distinction from cycads, even the i m m a t u r e c o n e s were open and the ovules occurred abaxially between the involute margins of a distal pelta (Harris, 1964). T h e ovules w e r e p l a t y s p e r m i c , with resin bodies in the sarcotesta.
Angiosperm Origins: Morphological and Ecological Aspects by V. A. Krassilov