MORPHOLOGY 
sion, the perianth consists of two sets of members, sepals and petals, 
which in general are foliar in nature, but differ more or less dis- 
tinctly from the ordinary bracts or leaves of the plant (fig. 562). They 
seem to have been derived, historically, from adjacent sporophylls and 
adjacent bracts or foliage leaves ; in any event, they are intercalated as 
distinct members between the bracts or foliage leaves on the one side, and 
the sporophylls on the other. It is not clear what was the most primi- 
tive condition of the flower among angiosperms; whether it began with 
O 
FIG. 563. Section of flower of peony, showing sepals (k), petals (c), numerous stamens 
(a), and apocarpous carpels (g). After STRASBURGER. 
a fully developed perianth, which in certain groups became reduced or 
even suppressed ; or whether it began with no perianth, which first ap- 
peared in very simple form an<igradually became more highly developed 
and complex. Both 'views have support. In any event, there are cer- 
tain general facts and tendencies of the flower which are evident. 
Differentiation of perianth. A series of flowers can be arranged with 
those having no perianth (naked) at one end, and those with a sharply 
differentiated calyx (sepals) and corolla (petals) at the other. Between 
these two extremes there will be found flowers with inconspicuous 
bracts, those with bracts more distinctly perianth-like in arrangement, 
those with a perianth differing in texture from bracts but not differen- 
tiated into two sets. It is evident that this series may have developed 
