pistillate

[Eng. pistil; -ate.] IMG:content-1136.png:[merged small][graphic] Bot . ( of a flower ): Having a pistil, or pistils, but rately to the bore of the tube; no stamens. IMG:content-1137.png:[blocks in formation] but the cylindrical form is almost exclusively employed for both, as in the common pump and the steam-engine. One of its sides is fitted to a rod, to which it either im parts reciprocatory motion, as in the steam-engine, or by which it is itself reciprocated, as in the pump. In the former case, it has no opening Piston. leading from one side to the other, and is termed solid, though generally not really so; but in the latter, an aper- A Piston. B. Piston. ture controlled by a valve permits the pa age of the fluid from one side to the other during its downward rod. C. D. Steam. ports. E. Slide-valve. F. Cysunder. movement. A distinction is, however, made in pumps; the solid piston being known as a plunger, the hollow piston as a bucket. The piston usually requires packing to cause it to fit closely within its cylinder and at the same time allow its free backward and forward movement.