210 



EVOLUTION OF PLANTS 



cese), as well as many others more or less familiar. 

 (Fig. 51, C, D.) 



The order Tricoccse, of somewhat doubtful affinity, in- 

 cludes the single family Euphorbiaceae with the various 

 species of Euphorbia as types. A few are cultivated, 

 like the familiar castor-bean (Ricinus), and the showy 



FIG. 51 (Higher Choripetalre) . A, wall-flower (Cheiranthus) : the parts 

 of the flower are definite in number ; B, the six stamens, the two outer 

 ones shorter than the others, and the pistil, car, made up of two cohe- 

 rent carpels; C, flower of Oxalis, the parts perfectly symmetrical, and 

 in fives; D, the ten stamens, an, in two sets of five each, and the five 

 carpels, st ; E, flower of a Spiraea, one side removed to show the five 

 free carpels, car, and the numerous stamens inserted upon the calyx 

 margin; F, flower of the common pea (Pisum), showing marked zygo- 

 morphy ; G, the ten stamens, one of them free, and the single carpel, car, 

 of the pea ; H, a flower of Fuchsia, with " inferior " ovary, o, and showy 

 colored sepals. 



Crotons and Poinsettia of the greenhouses. The 

 flowers in all Euphorbiacese are inconspicuous, but it 

 is common for them to develop showy bracts about the 

 clusters of flowers, and these serve the same purpose as 

 the showy petals of other Choripetalse. 



The most specialized as well as the most numerous 



