PART III. | THE MECHANISMS OF FLOWERS. 169 
_ show a slight, club-shaped thickening, which afterwards becomes 
- much more apparent ; the five inner, including the superior solitary 
_ stamen, remain unthickened throughout. The anthers, while yet 
fully twice as broad as the ends of the filaments, dehisce in the base 
_of the cone, completely filling it with pollen, and when they have 
"discharged their contents they shrivel up to a fourth of their former 
size. All the petals now grow to their full size, and the five 
_ outer stamens elongate and the ends of their filaments thicken, so 
: that, in spite of the continual growth of the carina, they still reach 
_ to the hollow cone formed by its apex, and completely fill its lower 
and wider portion notwithstanding that the five inner stamens 
_ have remained behind. When the flower has reached maturity, the 
essential organs occupy the relative positions shown in 8, Fig. 53. 
_ The five inner stamens (d) are useless after shedding their pollen, 
and, far outstripped in development by the other organs, they lie 
_ shrivelled up in the lower and wider part of the carina. The five 
| outer (e), which have still an important part to play, have continued 
- to grow, and lie with their thickened ends tightly closing in the 
_ base of the hollow cone now filled with pollen. Somewhat below 
_ the apex of the carina lies the stigma (7), and at the apex (near g) 
is a narrow opening; the entire space between the thickened 
_ filaments and the orifice is filled with compressed pollen, and thus 
} the piston-mechanism is complete. On the application of a slight 
| downward pressure to the carina, the thickened filaments are 
_ forced further into the apical cone of the carina, and squeeze a 
_ certain amount of pollen through the orifice in a narrow ribbon. 
_ When the pressure ceases, the thickened filaments, thus squeezed 
_ together, tend to spring apart, and so raise up the apical cone and 
_ restore the whole carina to its former position ; the elasticity of the 
_ carina itself assists in this action. If the carina be drawn or 
_ pressed still further down, the end of the style protrudes, covered 
_ with pollen, from the orifice. When the pressure ceases it returns 
again into the carina; but the edges of the orifice, which readily 
yield to a pressure from within and allow the stigma and pollen to 
pass out without hindrance, spring together and scrape off almost 
the whole of the pollen from the stigma as it returns within 
the carina. 
As soon as the piston-mechanism has become so far complete, the 
vexillum rises up perpendicularly so as to direct its broad, dark 
- surface straight to the front, and both the alz arch their 
_ surfaces into two hemispheres inclosing the carina, so as to strike 
| the eye equally well from before, from behind, or from either side. 
( 
