Ill] 



ROSACES 



37 



in others (Parastemon) the mesocarp is so thin that the 

 drupe is practically an Achene. 



In another series we find the bulging floral receptacle 

 taking part in the (false) fruit e.g. Potentillidese. In 

 Potentilla, &c. the torus is merely spongy, but in the 

 Strawberries it becomes fleshy and edible, and the whole 

 is an asterio of Achenes. In Potaninia there is only one 

 Achene on the hardly swollen torus. Next comes a group 

 with similarly bulging torus but bearing little Drupes 

 (Drupels), and the various species of Rubus (Blackberry, 

 Raspberry, &c.) give us examples of such an aeterio of 

 Drupels (Fig. 24). 



A further variation in Rosacese is brought about by 

 the depression of the carpels into the hollowed floral axis 

 (calyx-tube). In Geum the Achenes are situated on an early 

 flat torus, but in many of its allies it is sunk more and 

 more deeply and the calyx creeps up around the group of 

 achenes. In the Agrimony (Fig. 36) and Alchemilla the 



B 



Fig. 36. Agrimonia Eupatoria. A, fruit. B, fruit cut down the 

 centre (Bai). 



few achenes are thus closely enveloped by a hard calyx- 

 tube, but in the Roses the numerous achenes are at the 

 base of a fleshy calyx-tube, and the whole is termed a Hip. 

 In the Pomacese (Apples, Pears, &c.) we have yet 

 another series in which the enlarged calyx-tube is pro- 



