II. DESCRIPTIONS OF THE SEEDS OF THE COMMER- 

 CIAL BLUEGRASSES AND THEIR IMPURITIES. 



By F. H. HiLLMAN, 



Assistant Botanist, Seed Laboratory. 



THE BLUEGRASSES. 



The "seeds" of the species of Poa, or the bhiegrasses, are the 

 ripened florets or individual parts o'f the smaller clusters, or spikelets, 

 of the general floral system of the plant. The number of florets in 

 each spikelet varies from two to nine in the different kinds of Poa 

 commonly found in commerce. There is some variation in the num- 

 ber of florets in the spikelets of each species. The florets separate 

 readily at maturity, and well-cleaned samples of seed contain few 

 whole or partial spikelets. 



A complete, mature spikelet embraces, besides its several florets, a 

 pair of chafl'y scales, termed empty glumes, between which the florets, 

 or at least the lower ones, rest. The empty glumes, while somewhat 



Fig. 1.— I.— A spikelet of Poa: a, stem of spikelet: 6, empty glumes: c, florets, or "seeds." II.— FiTv'i 

 floret, back view: a, callus; 6, keel; o, intermediate veins; d, marginal veins; c, hyaline pori;. u : i 

 glume. III. — Single floret, side view: a, callus; 6, rachilla segment; c, keel; d, intermediate veil.; 

 e, marginal vein: /, margin of glume. IV. — Single floret, front view: <(. rachilla segmeut: b, mar- 

 ginal fold; c, palea: r/, keels of palea. V. — Terminal floret, front view: o, rachilla segment: /;, aborted 

 floret; c, palea. VI. — Caryopsis, or grain: «, location of embryo: b, keeled face; c, grooved face. 



dissimilar, are keeled, acute, and one or three veined. The keel of 



each is usually hispid-ciliate above the middle. A portion of the stem 



of the spikelet often remains attached to the base of the empty glumes 



when these are found in connnercial samples. 



Each mature, well-developed floret or seed consists of a caryopsis, 



commonly called grain, two inclosing scales which, together with 



the empty glumes, constitute the chart', and a slender appendage, 



the rachilla segment. (Fig. 1.) 



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