'44 GRASSES OP IOWA. 



The Flower. 



Parts of the flower. — The llowers of grasses possess only the 

 essential organs — the stamens and pistils. The bracts enclos- 

 ing these are modified leaves or leaf sheaths andprophylla. 

 Sometimes the stamans and pistils are separated, when the 

 flowers are either male or staminate (containing stamens only), 

 or female or pistillate (containing pistils only). These stami- 

 nate and pistillate flowers may occupy different parts of the 

 same plant or (more rarely) entirely distinct plants. Flowers 

 having both stamens and pistils are termed hermaphrodite. 



In each flower there are usually three stamens. These 

 have slender fi'aments, and usually versatile, sometimes basi- 

 fixed, two-celled anthers, which are pale yellow, sometimes 

 nearly white, or purple, or some shade of red. The pistil 

 consists of the ovary and usually two feathery or plumose 

 stigmas, which may be sessile or raised on short or long and 

 more or less divided styles. 



The fruit or ripened ovary constitutes the "grain." This 

 is a true caryopis, i. e., a dry one-seeded fruit in which the 

 outer covering or pericarp is closely adherent to the seed. 

 The "grass seed " of commerce consists of the grain 

 enveloped usually in more or less "chaff" (glumes and 

 paleas). 



Arrangement of the flowers. — The arrangement of the flowers 

 in grasses is peculiar. They are situated in what are termed 

 spikelets, either solitary (one flowered spikelets) or two 

 or more together (two to several or many-flowered spikelets). 

 Each flower is located in the axil of a chaff-like bract or glume 

 called the flowering glume (really a leaf-sheath). At the base 

 of the spikelet there are usually two bracts or glumes having 

 no flowers in their axils; these are the outer or empty glumes. 



Hackel, in his work on grasses, says: "The palea, which, 

 with its enclosed flower, stands opposite the flowering glume, 

 does not belong to the main axis of the spikelet, but to the 

 branch which bears the flower. That this relation of parts 

 may be gradually obliterated in the one-flowered grasses, and 

 that the palea may be moved back upon the main axis, has 

 been explained above. As long as an axis or a rudiment of 

 one, at least in its earlier stage, is visible beyond the palea, 

 this latter possesses (like the prophylla of the culm branches) 

 two keels, or at least two lateral nerves, without a mid-rib; 



