DEVE Str VONS OF THESSEEDS OF Dik COMMER: 
CHIlS DIEU RCRASSES AND hE TR INE URITTES. 
By F. H. Hitman, 
Assistant Botanist, Seed Laboratory. 
THE BLUEGRASSES. 
The ‘‘seeds” of the species of Poa, or the bluegrasses, are the 
ripened florets or individual parts of 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 chaffy 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; b, empty glumes; c¢, florets, or ‘‘seeds.’’ II.—Single 
floret, back view: a, callus; b, keel; c, intermediate veins; d; marginal veins; e, hyaline portion of 
glume. III.—Single floret, side view: a, callus; b, rachilla segment; c, keel; d, intermediate vein; 
e, marginal vein; f, margin of glume. IV.—Single floret, front view: a, rachilla segment; b, mar- 
ginal fold; c, palea; d, keelsof palea. V.—Terminal floret, front view: a, rachilla segment; b, aborted 
floret; c, palea. VI.—Caryopsis, or grain: a, 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 commercial 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 chaff, and a slender appendage, 
the rachilla segment. (Fig. 1.) 
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