421 
lions of these grains. They are observed to have a small circular cavity* 
or opening, through the outer surface as represented in fig. 11, plate II. 
Each grain is found to be a sack composed of two coats or coverings, 
within which is contained a transparent fluid filled with particles still 
more minute—supposed to be grains of starch. When moisture is ap¬ 
plied to the pollen grains, the inner coat expands and is protruded through 
the opening or weak place in the outer coat, and the contents are dis¬ 
charged with an explosive force. The minute grains thus liberated from 
the pollen sack will be seen in constant'motion resembling the motion of 
living animals. 
Plate 2. Figure 1. 
\ 
1. A panicle, at the time the seed is ripe, one-fourth the natural size. 
2. Extremity of a branch showing the staminate flowers, (natural size.) 
3. Staminate flower magnified. 
4. Anther, magnified. 
5. Germ and stigmas, magnified. 
6. Pistillate flo^ver. 
7. The same when ripe. 
8. The seed. 
9. A portion of the awn magnified. 
10. The rachis of the fertile flowers. 
11. Pollen grains very highly magnified. 
5. Zizania Milliacea. Michaux. 
Panicle diffuse, ample, the staminate and pistillate flowers intermixed; 
awns short; styles united ; grain ovate smooth; leaves involute. An¬ 
nual ; flowers in August. Culms 6 to 10 feet high. Grows in water. On 
Hoffman’s Prairie, and along the canal, near Dayton, Ohio. 
But little is known respecting this species, if indeed it is distinct from 
the last. It appears to be more common at the South, where it takes 
the place of our z. aquatica. 
GENUS 3. LEPTURUS. Robert Brown . 
From lepios, slender, and lira, tail, from the long slender spikes. 
Flowers in spikes, polygamous ; rachis filiform, jointed ; joints with 
one spikelet; glumes, one or two, growing to the rachis, simple, or two- 
parted. 
