DEVELOPMENT OF PLANTS 429 



(Rhamnus), Jersey tea (Ceanothus), used in revolutionary times 

 as a substitute for tea, the grape (Vitis), Japanese ivies, Virginia 

 creeper (Parthcnocissus) , etc. The minute green or white flower 

 shows a further reduction in parts, the petals not only being fre- 

 quently suppressed, but the stamens are reduced to one whorl 

 and placed opposite the sepals, whereas they alternate with the 

 sepals in the Sapindales (Fig. 321, E-G), and the nectary is 

 within the filaments. 



147. Myrtales, the Myrtle Order. This order marks a de- 

 cided advance in the evolution of the flower over preceding 

 groups, as indicated by the adhesion of the calyx and receptacle 

 and usually of the ovary, the flowers being perigynous and usu- 

 ally epigynous. Another important character is that the flowers 

 are always cyclic, the organs being regularly arranged in five 

 whorls of four or less commonly of five members each, though the 

 number of stamens may be greatly increased by the splitting of 

 the original number of the set. The petals are frequently sup- 

 pressed and the calyx is often highly colored, a variation to be 

 seen in many groups when the corolla is wanting. The carpels, 

 as a rule, contain numerous ovules (Figs. 322, 323). The Myr- 

 tales is an important tropical order and represented with us by 

 many familiar plants, such as the meadow beauty (Rhexia), wil- 

 low-herb (Eptiobium), the large evening primrose family, with 

 one of which, Oenotkera (Fig. 323, A, B), deVries worked out 

 his theory of mutation, and the common ditch and pond aquatics 

 the water milfoil (Myriophyllum) and mermaid weed (Proser- 

 pinaca) . 



The purple loosestrife (Lythrum) illustrates the characters of 

 the lower members of the order before epigyny has become estab- 

 lished (Fig. 322). The wand-like branches of this introduced 

 plant with their terminal spikes of purple flowers are becoming 

 rather common around the borders of marshes and water ways. 

 The cup formed by the calyx and receptacle bears on its rim 

 alternately with calyx lobes the rather twisted petals and at its 

 base eight to twelve stamens. The pistil is composed .of two 

 carpels. This flower has become historic because of the atten- 

 tion that has been given to its devices for crossing. Fig. 322 



