P. nemoralis, L., hardly differs from P. trivialis, but the paleæ are sub-acute, nerves obsolete, and scarcely hyaline at the margins. The “seed" is shorter and more acute, and the colour less pronounced, and with hardly a trace of hairs (Fig. [54]).
When the basal hairs are absent this should go with P. annua, &c. (see p. [146]).
It is practically impossible to distinguish these species by the "seed." Care is necessary to distinguish Kœleria, which is somewhat larger in size, keeled, compressed and nerved similarly, but is more pointed and curved and paler yellowish white in colour. Hard and devoid of web or hairs. Aira is distinguished by the awn: Agrostis by the very different paleæ and caryopsis.
The other Poas are devoid of web, though they may have hairs below, and require very careful examination. The whole group is excessively difficult to deal with in “seed," and a special study of it is needed, since several species are important, and it forms a type.
(b) No web or pencil of hairs below the “seed."
(1) Apex of palea rounded, blunt, notched, or at most bluntly pointed, but with no trace of awn-or bristle-tip.
✲ Palea inflated, round-backed and somewhat winged, membranous.
Briza media.
B. minor.
| Briza media. B. minor. |
Briza media, L.
Paleæ blunt, 2·5-3 mm., without lateral projections, markedly convex—almost conduplicate; nerves several. Caryopsis ovoid, 1·5-2·5 mm., dark brown.