DILLENIALES 433 



Australia, is of major morphological interest, because it shows in its 

 androecium the origin and modification of stamen fascicles. The various 

 species show all stages in the fusion of the numerous stamens to form 

 five fascicles, each with many stamens, and the reduction of the stamens 

 within each fascicle to few or one, with simultaneous reduction in 

 fascicle number until only one fascicle with few stamens remains. Re- 

 duction in fascicle number gives strong zygomorphy to the androecium, 

 but the corolla is only slightly modified. The bractlike nature of the 

 calyx is marked in some species where the lowest of the spirally ar- 

 ranged, unequal sepals is leaflike, the uppermost sepaloid. 



In wood structure, the Dilleniaceae show many primitive characters. 

 The vessels are solitary and largely scalariform (simply perforate in a 

 few advanced genera). The scalariform vessel elements, resembling 

 those of Eupomatia, are highly primitive, very long and long-tapering, 

 with many bars — up to 130. The wood parenchyma is mostly diffuse. 

 The fibers have bordered pits. The rays are heterogeneous and both 

 wide and narrow. 



Paeoniaceae 



The taxonomic position of Paeonia, as a member of the Ranuncula- 

 ceae, long was in question. The genus has been placed in the 

 Berberidaceae and in the Magnoliaceae. The suggestion that it should 

 be segregated as an independent, unigeneric family was made in 1830 

 and again, seventy years later. In the twentieth century, evidence from 

 cytology, floral anatomy, and ontogeny has given this change strong 

 support and shown that the new family belongs in the Dilleniales. 



In general flower structure, Paeonia differs from the genera of the 

 Ranunculaceae and the removal of the genus from this family is justi- 

 fied. In gross structure, the flower of Paeonia differs from that of afl 

 genera in the Ranunculaceae. The perianth is not sharply limited. The 

 phyllotactic spiral is continuous from leaves through bracts, sepals, 

 petals, stamen trunks, and carpels (in herbaceous species, reduction of 

 the carpels to very few may break the series). The receptacle is some- 

 what concave, in contrast to the convex apex in other genera, and a 

 prominent, lobed disc surrounds the gynoecium. The fasciculate sta- 

 mens mature centrifugally. The ovules are large, with a massive outer 

 integument, and are borne on placental projections. The nuceflus is 

 absorbed before flowering, so that the inner integument encloses the 

 embryo sac. The micropyle is closed, and the seed coat has three major 

 layers. (Other genera have one or two layers.) Pollination is largely — 

 in woody species, perhaps wholly — by beetles. Beetles lick the lobes 

 of the prominent fleshy disc. The disc is, anatomically, a part of the 

 androecium; the lobes receive vascular supply from the stamen trunks. 



