186 BRITISH PLANTS 
fruits belonging to the Natural Orders Composite, Um- 
bellifere, and Amaryllidacee. 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 Composite 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 isnot 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. 
93 Bay a The following classification is a com- 
F . 5 
a snecion, 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. 
(6) 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 
