_Arrhenatherum avenaceum_, Beauv. (Fig. 47). Paleæ papery, ribbed. Awn 13-15 mm., twisted below; paleæ, with a tuft of hairs below and a ciliate keel, investing the fruit: the whole being cylindrical, 8-10 mm. × 1·5. Caryopsis 4-5 mm. × 1·2, fusiform, pubescent. Rachilla hairy. The distinctive difference between _Avena_ and _Arrhenatherum_ is in the spikelets as a whole. The latter has the lower flower of each spikelet male only. Samples contain the “double seeds,” and the awn of the upper fertile portion is short (see Fig. 69). †† _Caryopsis not more than 3 mm. long. A tuft of hairs on rachilla and base._ _Avena flavescens._ _Aira flexuosa_, distinguished by its nearly basal awn, harder texture and darker colour of paleæ, and _Dactylis_--awnless and with curved long drawn-out apex--are found as impurities in foreign “seed.” [Illustration: Fig. 69. _Avena flavescens. c_, “seed,” nat. size; _a_ and _b_, ditto, × about 7. The dorsal twisted and kneed awn is very characteristic. Note also the hairy rachilla. The palea is bifid above--not visible in the lateral view. Nobbe.] _Avena flavescens_, L. (Fig. 69). Yellow. Palea about 5 mm. long, five-ribbed, bifid at the apex into two long slender teeth, closely investing the brownish caryopsis, and with a sub-dorsal awn 10 mm. long with little or no twist, and hairy at the base. Rachilla flattened and with white hairs. Caryopsis not much grooved, fusiform, 2-3 mm. long, glumes unequal, somewhat keeled and rough. (2) _Awn dorsal or basal, fine and hair-like, and little or not at all twisted or kneed. “Seed” small._ * A pencil of silky hairs on base or rachilla. Palea bifid at the tip. † _Basal hairs longer than palea, and obscuring the awn._ _Calamagrostis Epigeios._ Of little importance. _Digraphis_ has no awn. _Calamagrostis Epigeios_, Roth. Palea about 3 mm. long with toothed apex and very thin caryopsis 1 mm. A conspicuous tuft of fine silky hairs, longer than the palea at the base and on the rachilla. Awn slender, dorsal, about as long as the palea. _C. stricta_, Nutt. and _C. strigosa_, Hartm. are rare. †† _Basal hairs shorter than palea._ ⊙ _Awn brown, bearded in the middle, thickened and white above._ _Aira canescens._ The student will find considerable difficulties in the various species of _Aira_ and _Agrostis_, owing to their small size and variability as regards awn and basal hair-tufts. All these are weeds, but some occur as adulterants. _Aira canescens_, L. “Seed” (apart from the awn, it is very like _Agrostis_) 1·5-2 mm., with a very thin, smooth, keeled, two-nerved palea, bifid at its apex, through which the yellow caryopsis shines. Awn slender, basal, dark-brown, with oblique colourless hairs above the middle and with a slight swelling above.