186 BRITISH PLANTS 



fruits belonging to the Natural Orders Composite, Um- 

 belliferse, and Amaryllidaceae. An inferior ovary, how- 

 ever, is always, to a greater or less extent, merged with 

 the receptacle, and, strictly speaking, all such fruits 

 should be called " false." The true achene is a fruit 

 derived from a one-seeded superior ovary. It is dry and 

 indehiscent. In the Compositse the fruit is one-seeded 

 and indehiscent, but it is the product of two carpels and 

 an inferior ovary. The ovule is basal, arising from the 

 receptacle ; the carpels merely roof in the chamber at the 

 top. The fruit, therefore, is actually more receptacle 

 than carpels, and is, therefore, not a true fruit at all. By 

 calling it a cypsela the difficulty is not faced. Biologically, 

 of course, it is an achene. In other inferior ovaries the 

 ovary is sunk in the receptacle, and the carpels line the 

 chamber of the fruit, but do not constitute 

 the whole of the fruit-wall e.g., narcissus. 

 This illustrates some of the difficulties 

 in the way of any strictly morphological 

 classification of fruits, and a purely 

 biological division is equally unsatisfac- 

 tory, since it classes together fruits of the 

 most diverse origin and development. 

 The . followin g classification is a com- 

 DANDELION. promise. It is to be regarded as one of 

 convenience only, sanctioned to some 

 extent by custom and practice, but neither logical 

 nor strictly scientific : 



I. Dry Fruits, formed by the carpels alone, or, if the 

 receptacle plays any part at all, it is insignificant. 



1. Achenial Fruits. Pericarp dry, indehiscent, one- 

 seeded. 



(a) Achene, derived from a one-seeded ovary. 



(b) Nut, derived from a several-seeded ovary. 



Here the achene (Gr. a, not ; chenos, a splitting) is used 

 in a wide biological sense, and includes all one-seeded 

 fruits, whether inferior or superior, or formed of one or 

 more carpels. The term is thus made to include such 

 varieties as the cypsela (inferior fruit, Fig. 82), the 

 caryopsis (fruit superior, but pericarp fused with the seed 

 e.g., grasses), and the samara, or key (the winged achene 

 of the ash, Fig. 83). As the fruit contains only a single 



