THE ARCHICHLAMYDE^: 399 



1. The tree orders, including the willows and poplars (Sali- 

 cales); the walnuts and hickories (Juglandales) ; the birches, 

 alders, beech, chestnut, and oaks (Fagales); the elms, figs, mul- 

 berries, etc. (Urticales). 



2. The buttercup order, Ranunculales, a large assemblage of 

 about 4000 species, full of interesting gradations in floral evolu- 

 tion, the buttercup family (Ranunculacece) being an especially 

 good group for such studies. 



3. The poppy order, Papaverales, comprising the poppies and 

 the large mustard family. 



4. The rose order, Resales, an immense group of over 14,000 

 species, with several large families, such as the legume or pea 

 family, the rose family, etc. The flowers present a greater range 

 of structure than in the buttercup order. Some large groups in 

 the legume family have flowers with well-developed bilateral 

 symmetry and dorsiventrality. 



5. The geranium order, Geraniales, containing the geraniums, 

 flax, Euphorbias, etc. 



The violet order, Violates, comprising a large number of 



.es and more than 4000 species. 



The cactus order, Cactales, a very remarkable American 

 group of more than 900 species, mostly adapted to desert 

 conditions. 



8. The umbel order, Umbellales, containing more than 2500 

 species, mostly in the umbel (parsley) and dogwood families, 

 the highest order in the series of the ArcMchlamydece on account 

 of its epigynous flowers, the reduced number of carpels, and the 

 massing of the flowers in the characteristic umbel, or in close 

 heads surrounded by a corolla-like involucre of bracts, as in the 

 dogwoods (Cornacece, see Frontispiece). 



373. The Metachlamydeae. The general flower characters of 

 this sub-class are cyclic arrangements of parts with definite 

 numbers, perigyny or epigyny, and a reduced number of carpels 

 in the compound pistil (syncarpy). The corollas are usually 

 showy, the petals being borne on tubular or cup-like outgrowths 



