. Bulletin. 1901-13. Agriculture; Agriculture. THE BLUEGRASSES. 17 most species are thin and translucent, or hyaline. The extent of the hyaline portion of the apex has much to do with the form of the latter and is variable in the different species. The palea is commonly more delicate in texture than the glume, being partially hyaline. It usually is shorter than the glume, but in some species equals or exceeds it in length. The difference in length usually is most evident in the lower florets of the spikelet. Two veins traverse the palea lengthwise and nearly meet at its apex. The mar- gins of
. Bulletin. 1901-13. Agriculture; Agriculture. THE BLUEGRASSES. 17 most species are thin and translucent, or hyaline. The extent of the hyaline portion of the apex has much to do with the form of the latter and is variable in the different species. The palea is commonly more delicate in texture than the glume, being partially hyaline. It usually is shorter than the glume, but in some species equals or exceeds it in length. The difference in length usually is most evident in the lower florets of the spikelet. Two veins traverse the palea lengthwise and nearly meet at its apex. The mar- gins of the palea are more or less acutely infolded along these veins, which are called the keels of the palea. The keels are mostly covered by the glume in some species, while in others they are almost wholly exposed. There is some variation in this respect, however, among seeds of the same species. The apex of the palea is often notched. The rachilla segment is nearly cylindrical and usually somewhat curved. It is slightly expanded at the apex, which is obliquely trun- cate, its terminal surface constituting the scar of at- tachment to the succeeding floret. Different florets in the same spikelet in certain species exhibit a marked variation in the length of the rachilla segment, which is shortest in the lower florets and conspicuously longer in the terminal one, where it usually bears an aborted floret as a small, pointed appendage. The surface of the florets of different species of Poa is subject to considerable variation. Some florets are smooth, or glabrous; others bear numerous minute, ,./« i_ l • £ i_ u FIG- 2.—Unrubbed stifhsn hairs, rendering the surface rough, or scabrous; Kentucky biue- and some have a fine, appressed pubescence covering grass seed (Poa a part of the surface. Most of the species have a ?,'"pubescenceU'of more or less silky pubescence on the keel and mar- marginal vein: c, ginal veins below the middle or somewhat higher on j^i*5 the keel. Th
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