_Alopecurus_ is very characteristic, and should be carefully examined as a type. _A. pratensis_ is a valuable grass and said to be often adulterated with the undesirable _A. agrestis_, _Holcus_, &c. _Arrhenatherum_ and _Avena_ are easily distinguished by the basal hairs, rachilla, &c. [Illustration: Fig. 68. _Alopecurus pratensis. a_, “seed,” nat. size, and _b_, _c_, ditto, × 8; _d_, caryopsis, × 7. The “seed” here consists of the two glumes, connate below and hairy on the keel and ribs, including the caryopsis enveloped in a single palea with a dorsal awn. Note remains of stigma in _d_. Nobbe.] _Alopecurus pratensis_, L. (Fig. 68). Inner palea absent. Outer palea 5 mm., caryopsis 3 mm. long, often with remains of the stigma. The greyish-brown spikelet of _Alopecurus_ easily falls as a whole, included in the glumes; the palea is loose and delicate. Glumes connate below, silky-hairy on keel and ribs all the way up. The palea has a bent dorsal awn, about 5 mm. long. _Alopecurus geniculatus_, L. Palea 2 mm., fruit 1·3 mm. long. The glumes hairy on ribs and keel as in _A. pratensis_: glumes more obtuse. _Alopecurus agrestis_, L. Palea 6 mm., fruit 3 mm. long. Glumes only ciliate, on ribs and keel, except at the base where the hairs are longer. Keel slightly winged. Best distinguished from _A. pratensis_ by the glumes, which are smoother, broader above the middle, harder and with a few basal hairs. The species _A. fulvus_, _A. bulbosus_, and _A. alpinus_ are rare. (ii) “Seed” consisting of the paleæ investing the caryopsis, freed from the glumes. * _Palea at least 14 or 15 mm. long: caryopsis 5-7 mm. [Oat type.]_ _Avena fatua._ _A. pratensis._ _Avena fatua_, L. Palea parchment-like, lanceolate-terete, acuminate and bifid at the apex, rounded on the back and with yellow hairs on the lower part. 15 × 3 mm. Awn brown, twisted and bent, arising from the middle, about 30 mm. long. Caryopsis 7 mm. long, hairy at the top and distinctly grooved. Rachilla with fine bristles. _Avena pratensis_, L. Palea very similar to _A. fatua_, apex 2--4-toothed or bifid, rachilla with stiffer hairs. Caryopsis about 5 mm. long. _Avena pubescens_, Huds. is a variety of _A. pratensis_ found on dry calcareous soils. The caryopsis is very narrow, and the rachilla long and feathered with hairs. “Seed” shorter than _A. pratensis_, 10-13 mm., and darker in colour. _A. fatua_ is an excellent type of the grasses with dorsal twisted and bent awns, and easily examined on account of its size. The student will find difficulties with other species of _Avena_ and _Arrhenatherum_. Harz says the stiff hairs of _Avena_ bring about the formation of intestinal concretions (phytobezoars) and are therefore dangerous to domestic animals. ** _Palea not more than 7-10 mm. long._ † _Caryopsis 4-5 mm. long._