The other varieties of _F. elatior_ cannot be distinguished by the “seed” alone: in my samples _F. elatior_ proper is longer than _F. pratensis_, and both have occasionally a trace of awn. Var. _arundinacea_ has a more acuminate, stiff point. _Festuca pratensis_ has its palea as a rule somewhat more acute than _Lolium perenne_, and the flatter tapering rachilla of the latter is more closely appressed to the palea. The caryopsis of _Festuca_ also tends to adhere to the paleæ. ⊙⊙ _Paleæ and “seed” at most 3-3·5 mm. long._ ≡ _Palea devoid of hairs or keel, notched or blunt, and with no trace of awn._ Δ _Palea hyaline, nerves indistinct. Tips notched or blunt._ _Agrostis alba._ There is occasionally a very short basal hair (awn). _Agrostis_ and _Aira_ will present difficulties to the beginner, not only on account of their small sizes, but also from the variability as regards awns, basal hair-tuft, &c. None are of value, and most of them are weeds. _Agrostis alba_, L. (var. _stolonifera_). Palea enclosing the fruit 1·8-2 mm. long, white, delicate, membranous, with a blunt notched apex and three (or five) nerves: occasionally there is a fine kneed basal awn, not projecting. The glumes may remain attached: the outer has a serrulate keel, and often a violet hue. No awn. About 2-3 mm. Caryopsis about 1·1 mm. long, oblong, yellow, corn-shaped, furrowed, shining through. _A. vulgaris_, L., is a variety with slightly smaller fruits, no awn, and usually three nerves to the palea, but they cannot be distinguished with certainty by the “seed.” Rachilla obsolete. The colour of the glumes may vary considerably and is sometimes yellow. The absence of awn, rachilla, and basal hairs distinguishes _Agrostis_ from _Aira_. ΔΔ _Palea membranous, ribbed, tips scarious._ _Glyceria aquatica._ _G. fluitans._ _Glyceria aquatica_, Sm. Palea strongly 5-7 ribbed, obtuse and scarious, about 4 mm. long. Green with a purple cast. Caryopsis dark-brown, about 2 mm. long. Inner palea punctate. Rachilla slender and cylindrical. _Glyceria fluitans_, Br., is very similar, but longer (6 mm.) and more slender; the palea scabrid with truncate or ragged tips, and the inner palea not punctate. Yellow. (Fig. 46.) _Glyceria aquatica_ and _G. fluitans_ are sweet grasses of value in water-meadows only. The “seed” is not often met with. Not only with the Poas, but also with _Catabrosa_ are there difficulties in determination. _Molinia_ and _Kœleria_ also present difficulties with _Glyceria_: the former has fewer and feebler nerves. _Digraphis_ and _Arundo_ are easily distinguished by the basal hairs. ≡≡ _Palea acute and somewhat compressed and keeled, and with hairs on the ribs. Tips nerved._