280 MORPHOLOGY 
16, 17. (9 families, 2760 species.) These families are clearly special 
branches from Ranales, the most specialized one probably being the 
mustards (Cruciferae). 
18. Resales (16 families, 14,270 species). This is the greatest 
alliance among the Archichlamydeae, including far the largest family 
the Leguminosae, with over 11,000 species. Another prominent 
family is the Rosaceae, which gives name to the alliance. These two 
families are plainly branches from the Ranales; and among the Legu- 
minosae the flowers become conspicuously irregular. The irregularity 
is of a special type, illustrated by the sweet pea, so that a large part of 
the family is easily recognized. In the development of irregularity in 
connection with insect pollination, the Leguminosae hold the same 
position among Archichlamydeae that the orchids (Orchidaceae) hold 
among monocotyledons. 
19-25. (99 families, 27,358 species.) This is a tangle of seven 
alliances leading off in every direction from the preceding ones, each 
alliance characterized by some special feature. Each one, however, 
gradually becomes more definitely cyclic and approaches the epigynous 
condition. 
26. Umbellales (3 families, 2660 species). This is easily the highest 
of the alliances of Archichlamydeae and it is kept from being included 
among the higher Sympetalae only because it is polypetalous. The 
dominant family is the parsley family (Umbelliferae), and associated 
with it are the dogwoods (Cornaceae). The floral formula is definitely 
as. follows: sepals 5, petals 5, stamens 5, carpels 2, and this is also the 
most advanced floral formula found among Sympetalae. Associated 
with this high formula is epigyny. Another high character is that the 
flowers are small and massed, the cluster being more or less invested 
by a rosette of bracts (involucre). Apparently as a result of the 
massing of the flowers, the sepals are much reduced, and the whole 
cluster shows more or less division of labor, some flowers (the peri- 
pheral ones) often being more showy, and the others more fertile. 
SYMPETALAE 
This is a much better defined group than the Archichlamydeae, from 
which they are certainly derived. The combination of characters is 
as follows : completely cyclic flower, sympetalous corolla, ovule with 
a single massive integument, and complete absence of wall tissue in 
the ovule (see p. 263). About 42,000 species and 51 families are recog- 
