DICOTYLEDONS : ARCHICHLAMYDEAE 241 



one only is developed, the bud in the axil of the other 

 leaf being suppressed, and giving origin to a monochasial 

 cyme or cincinnus (Fig. 165, 3). The flower is typically 

 pentamerous, i. e. its parts are in whorls of five each, and 

 the floral formula is K5, 05, a 5 + 5, g (i). 



Many modifications, however, are met with, and the 

 plants of the order may be divided into two groups : 

 (1) A higher group which includes the Pinks, Catchflys, 

 and Campions, and (2) a lower group in which are the 

 Stitchworts, Chickweeds, &c. 



The floral diagram of a Campion (Lychnis) is shown in 

 Fig. 165, 1. Note that the stamens of the innermost whorl 

 are opposite the sepals, and the outermost whorl stands 

 opposite the petals. This arrangement (also found in the 

 Wood Sorrel) is said to be obdiplostemonous (L. ob = 

 inverse, Gr. diploos = double, stemon = a. filament). The 

 outer stamens are formed first, and ripen before the inner 

 ones. 



Cut a flower vertically, and note the arrangements of 

 its parts. The five sepals are united to form a tube (gamo- 

 sepalous), the internode between the calyx and corolla 

 has elongated and raised the corolla, stamens, and carpels 

 on a stalk (androphore) (Fig. 165, 4 and 5). The corolla 

 has five free petals, the limb often divided. In the Red 

 Campion there is an outgrowth at the junction of limb 

 and claw of each petal, forming together a corona (Fig. 

 165, 4 and 5, co). 



Note the arrangement of the ten stamens. The anthers 

 are ripe before the stigmas (proterandrous) . Look for the 

 nectary at the bases of the stamens. The pistil has five styles, 

 the ovary consists of five carpels, syncarpous, and one-celled. 

 (In Silene there are only three carpels.) Cut transverse and 

 longitudinal sections of the ovary and note the free-central 

 placenta on which are numerous ovules. The gamosepalous 

 calyx and long, narrow flower-tube exclude all but the long- 



1296 Q 



