INDEI1ISCENT APOCARPOUS FRUITS. 



261 



carpel When the pericarp is extended in the form of a winged 

 appendage, a Samara (samera, seed of Elm) or samaroid achcenium is 

 produced, as in the Ash (fig. 437), common Sycamore (fig. 465), and 

 Hirasa (fig. 466). In these cases, there are usually two achasnia 

 united, one of which, however, as in Fraxinus oxyphylla (fig. 437), 

 may be abortive. The Wing (fig. 465 a) is formed by the carpel, and 

 is either dorsal, i.e. a prolongation from the median vein (fig. 465 a), 

 or marginal, that is, formed by the lateral veins (fig. 466 a). It sur- 

 rounds the fruit longitudinally in the Elm. When the pericarp be- 

 comes so incorporated with the seed, as to be inseparable from it, as 



in Grains of Wheat, Maize, Rye (fig. 467), and other grasses, then the 

 name Caryopsis or Cariopsis (xx^vx, a nut, and &]/is t appearance) is 

 given. 



543. There are some fruits which consist of two or more achaania, at 

 first united together, but which separate when ripe. Of this nature 

 is the fruit of the Tropaaolum or Indian Cress, also that of Labiatae 

 and Boraginacese, which is formed of four achaenia attached to the 

 axis (fig. 402), whence the common style appears to proceed. Some 

 of these are occasionally abortive. In the ripe state the pericarp 

 separates from the seed in these cases ; and thus there is a transition 

 from indehiscent achasnia to single seeded dehiscent pericarps. So 

 also the Cremocarp (K^^XU, to suspend), or the fruit of Umbellifera3 

 (fig. 454), which is composed of two achsenia united by a commissure 



Fig. 465. Seed-vessel of Acer Pseudo-platanus, composed of two samaras or winged raono- 

 spermous carpels united, a, Upper part forming a dorsal wing. I, Lower portion corresponding 

 to the loculaments. 



Fig. 466. Samara taken from the fruit of Hiraea. s, Persistent style. I, Part corresponding to 

 the loculament a a, Marginal wing or ala. 



Fig. 467. Caryopsis of Secale cereale, Rye. 1. Entire. 2. Cut transversely to show the seed 

 adherent to the parietes of the pericarp. 



