490 



HUTCHINSON'S POPULAR BOTANY 



FIG. 612. MYRTLE-LEAVED ORANGE (Citruf 



aurantium, var. ). 



A hesperidium. 



(fig. 615). In form it is a 

 compressed oval, and is en- 

 closed, firstly, in certain chaffy 

 scales, which are easily separ- 

 ated from it ; then the mem- 

 branous pericarp or ovary ; and 

 within that, the testa, which is 

 the outer integument of the 

 seed, and to which the pericarp 

 closely adheres. Thus a grain 

 of wheat is not merely a seed. 

 It consists of a pericarp as well 

 as seed, and consequently is a 

 true fruit. Fig. 617 shows one 

 of the caryopses of a curious 

 Indian Grass (Coix lachryma), 

 popularly known as Job's Tears. 

 The peculiar heavy grey pearly fruits, hanging in clusters out of their 

 sheaths, give this plant a unique appearance. 



It is to be noticed that the caryopsis only differs from the achene 

 in one particular. In the former, the pericarp is closely adherent to 

 the testa of the seed ; in the latter there is no adhesion whatever. Both 

 are superior fruits (the ovaries being free from and rising above the 

 perianth) ; and in this respect, and this only, they differ from the cypsela, 

 which is inferior. 



The cypsela is the characteristic fruit of the great order of Composites ; 

 and its usual addition of a stipitate or sessile pappus admirably adapts 



it for dispersion by the wind 

 (figs. 610, 616). Johnston's 

 Botany of the Eastern Borders 

 contains some apposite re- 

 marks on the wind dispersion 

 of plumed cypselas, and use- 

 fully supplements what has 

 been already said on this sub- 

 ject in our preliminary re- 

 marks. " Elevated on the apex 

 of a long beak," says this 

 writer, " the parachute of the 

 seed of the G-oatsbeard (Tra- 

 gopogon pratensis) consists of a 

 number of slender spokes, 

 which diffuse themselves 

 circularly, and are ' telarly 



FIG. 613. URCHIN CROWFOOT 



(Ranunculus arvensis). 

 An achene. The second figure shows the fruit and seed in sectii 



