This troublesome weed (Couch-grass) presents similar difficulties with _Lolium perenne_ that _Agropyrum caninum_ does with _Lolium temulentum_--see p. 168. It is moreover extremely variable. _Dactylis glomerata_, L. (Fig. 64). Stiff awn-point just below the two teeth of apex of pale. Rachilla dilated above. Paleæ 5-6 mm. long exclusive of point, compressed and inflated, ribbed and ciliate-bristly on keel, the tip incurved. Caryopsis yellow-brown, ellipsoid, 2 mm. An important grass, said to be adulterated with _Lolium_, Fescues, _Holcus_, _Molinia_, _Bromus_, &c., most of which should be readily detected. The curved tip is an important distinctive character. _Cynosurus_ and _Festuca arundinacea_, _F. ovina_ and _F. rubra_ present resemblances. The seed is larger than that of _Poa_. _F. ovina_ and _F. rubra_ are smaller, rounded dorsally, and have no keel or cilia: the nerves are less prominent and the rachilla smaller. _Sesleria cærulea_, Ard. Palea distinctly toothed at the apex, making it almost three-lobed and very characteristic; with awn-point; five ribs, serrulate. Fruit grey-yellow, obovate. It is a mountain-and moor-grass of little value. +B. “Seed” awned--i.e. the investing palea bears, or tapers into, a distinct bristle or hair at least as long as itself or nearly so.+ (_a_) Awn not terminal. (1) _Awn stout, either obviously twisted and bent or “kneed.”_ (i) “Seed” consisting of the glumes as well as paleæ investing the caryopsis[13]. ⊙ _Awn bent but not twisted; glumes free below, ribbed, and with stiff short hairs on the keel._ ≡ _Awn sub-terminal, shorter than the palea, hooked._ _Holcus lanatus._ “Yorkshire Fog,” of little use or importance, except that it is frequently found as an impurity of other hairy grasses--e.g. _Alopecurus_. It cannot easily be confounded with any other grass: _Anthoxanthum_ and _Alopecurus_, _Arrhenatherum_, &c. present superficial resemblances only. These glumed hairy “seeds” are uncommon and form an easily recognised type. [Illustration: Fig. 65. _Holcus lanatus_. _a_, “seed”--i.e. complete spikelet--and ditto devoid of glumes, nat. size; _b_, spikelet, and _c_ the same devoid of glumes, × 7. The “seed” is here composed of the keeled glumes enclosing two pairs of paleæ and their flowers (_c_): the upper of these is barren and has a hooked sub-terminal awn to its outer palea. The lower awnless one is fertile. Nobbe.] _Holcus lanatus_, L. (Fig. 65).