LA W OF PROGRESSIVE COLOURA TION, 25 



The very earliest types of angiospermous flowers 

 now remaining are those in which the carpels still 

 exist in a separate form, instead of being united into 

 a single compound ovary. Among Dicotyledons, the 

 families, some of whose members best represent this 

 primitive stage, are the Rosacece and Ranunculacece ; 

 among Monocotyledons, the Alismacece. We may 

 conveniently begin with the first group. 



FIG. 5. Flower of cinquefoil (Potentilla). Primitive yellow. 



The roses form a most instructive family. As a 

 whole they are not very highly developed flowers, 

 since all of them have simple, open, symmetrical 

 blossoms, generally with five distinct petals. But of 

 all the rose tribe, the Potentillece, or cinquefoil group, in- 

 cluding our common English silver-weed, seem to make 

 up the most central, simple, and primitive members 

 (Fig. 5). They are chiefly low, creeping weeds, and 

 their flowers are of the earliest symmetrical pattern, 



