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 spikeletin 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 usuatly 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, 
stiffish hairs, rendering the surface rough, or scabrous; Gee oe 
and some have a fine, appressed pubescence covering grass seed (Poa 
a part of the surface. Most of the species have a }”cunewenes of 
more or less silky pubescence on the keel and mar- marginal vein; ¢, 
ginal veins below the middle or somewhat higher on = Pupescence & 
the keel. The intermediate veins are more rarely 
pubescent. The keels of the palea are usually fringed with minute 
hairs, or are hispid-ciliate, but in some species they are silky pubes- 
cent. The basal web is wholly wanting in some species and in others 
varies from a few fibers to a copious tuft. It readily separates from 
the floret in most species. The rachilla segment is usually smooth, 
but in some species it is appressed pubescent. The presence of the 
hairs on the marginal veins often necessitates that care be used in 
examining the rachilla segment with respect to pubescence. (Fig. 2.) 
The color of mature seeds varies from very light brown to dark 
brown. Sterile seeds are usually lighter or straw colored. Immature 
seeds are more or less tinged with green; some are purplish. In cer- 
tain species the glume is tinged with golden yellow near the apex. 
The aborted terminal floret and all the hairs are white. The rachilla 
segmént is lighter colored than the glume or palea. 
5813— 
