458 DICOTYLEDONES. 



2. POTENTILLE.E (Figs. 494, 496, 497). The flower has an 

 " epicalyx " (Fig. 494 C) alternating with the sepals and formed by 

 their stipules which are united in pairs, and hence its leaves are 

 often more or less deeply bifid. The receptacle is cupular and 

 often quite insignificant. The sepals are valvate in the bud. The 

 large number of fruitlets are achenes, borne on a well-developed 

 convex portion of the receptacle (the Ranunculeae resemble the Poten- 

 tillefe, but Lave no epicalyx, no enlarged receptacle, and spirally-placed stamens). 

 Most of the species are herbs with dichasial inflorescences, often 

 arranged in racemes. Potentilla (Cinquefoil). The achenes are 

 borne on a dry, hairy receptacle ; the style is situated towards the 

 apex of the ovary, and is not prolonged after flowering. Herbs 

 with digitate, in some, however, pinnate leaves, and generally yellow 

 flowers. Comarum (Fig. 494) (Marsh Ciuquefoil) forms, by its 

 fleshy-spongy receptacle, a transition to the next genus. Fragaria, 

 (Strawberry) (Fig. 496). The receptacle becomes finally fleshy, 



496. A 



FIG. 49C, 497. Fragaria vesca. 



FIG. 49C. Longitudinal section of flower. 



FIG. 4a7. A carpel, entire, and in longitudinal section. 



coloured, and falls off (biologically it is a berry) ; the numerous 

 fruitlets (drupes with thin pericarp) have basal styles (Fig. 497) ; 

 leaves trifoliate ; long, creeping runners. Geum (Avens) has a 

 terminal style which after flowering elongates into a long beak, 

 with the apex (after the uppermost part has been thrown off) bent 

 back into a hook, thus furnishing a means of distribution for the 



fruits. Leaves pinnate. Dryat comprises 3 Arctic or Alpine species with 

 simple leaves and solitary flowers, the calyx and corolla 8-y-merous, the fruit 

 resembles that of Geum, but the styles become still longer and feather-like 

 (a Hying apparatus). 



3. RUBE.E. liubus (Bramble) has the same form of receptacle 

 as the Potentilletv, but no epicalyx; the fruitlets are drupes, not en- 

 closed by the persistent calyx. Most frequently shrubs or under- 



