THE FRUIT: INDEHISCENT FRUITS 



189 



buttercup flower when ripe make a head of akenes, which form 

 the fruit of the buttercup (fig. 147). Other examples of akenes 

 are found in other members of the buttercup family, also in the 

 composites, etc. The sunflower seed is a good example of an 

 akene. It should be borne in mind that the sunflower " seed " 

 (and " seed " of other composite flowers) is a fruit containing the 

 seed. 



312. The samara. The samara is a dry fruit, with a thin 

 membranous expansion extending more or less around the edge, 

 somewhat resembling wings, which 



serve to float the seed and aid in dis- 

 tribution by the wind. The "winged" 

 fruits of the maple, box elder (fig. 149), 

 elm, etc., are examples. They are 

 sometimes called " key^" fruits. 



313. The caryopsis is a dry fruit 

 in which the seed is united with the 

 pericarp (wall of the ovary), as in the 

 wheat, corn, and other grasses. It is 

 perfectly proper to say " seed wheat," 

 " seed corn," " grass seed," etc., if it 

 is understood that these grains are 

 fruits including the seed. It would be 

 absurd to insist that in all such cases 

 one must avoid the use of the term seed 

 when speaking of the grains and of 



akenes, and use instead sunflower fruit, wheat fruit, corn fruit, 

 grass fruit, etc., or oat fruit and barley fruit. In the latter 

 " seeds " not only are the seed coats united with the pericarp, 

 but this is firmly enclosed within the palae of the flower. 



314. The schizocarp is a dry fruit consisting of several united 

 carpels (compound pistil) which splits at maturity in such a way that the 

 carpels separate from each other but do not themselves dehisce and free the 

 seed, as in the carrot family, mallow family. 



315. The acorn. The acorn fruit consists of the acorn and 

 the " cup " at the base in which the acorn sits. The cup is a 



Fig. 149. 



A winged fruit, a samara, 

 fruit of the box elder. 



