_Hordeum_--Barley, 10, 20, 22, 26, 44, 59, 88, 89, 90, 92, +99+, 100, 108, 127, 134, 163; _H. jubatum_, 125; _H. maritimum_, 8, 10, 29, 33, 59, +100+, +163+; _H. murinum_, 8, 10, 14, 21, 30, 50, +59+, +76+, +100+, 125, 162, +163+; _H. pratense_, 7, 11, 14, 21, 22, 28, +58+, +100+, +163+; _H. sylvaticum_, 7, 11, 14, 28, 34, 44, +58+, 59, +100+, 105, +162+ Humus species, 33, 35 Hybrids, 120 Hydrophytes--plants requiring much water, and therefore aquatic or semi-aquatic, 37 Hygrophilous species--hydrophytes, 70 Imperfect--rudimentary or staminate, 105 Inconspicuously awned grasses, 93 Indicator-plants, 31, 32, 34 Inflorescence, _5_, _9_, _12_, _15_, 83, +86+-+91+, 97, 99, 102, 103, 105, 106, +109+-+118+, 119 Infolding of leaves, 20, 23, 25, 62, +63+, 64 Inrolling of leaves, 20, 23, 25, 46, 62, +63+, 64, _65_, _66_, _67_, _69_, 75, 78, 79, 80 Intercellular spaces, 37 Internode, 8, 17 Intra-vaginal shoots, 12, 13 Introduced grasses, 30 Involute--rolled inwards, 20, 47 Irritability of seedlings, 132 Italian Rye-grass--_Lolium italicum_ Keel, 18, _23_, 26, _63_, 68, 69, 91, 113, 127, 140, 144, 146, 147, 148, 149, 151 Keeled grasses, 26, 74 _Knappia_--_Mibora_ Kneed awns, _129_, 130, 151, 153, _154_, _158_ Kneed stem, _9_ Knot-grass--_Polygonum_ _Kœleria_, 11, 14, 19, 20, 25, 26, 90, 91, 92, 101, 103, 110, 141, 146, _149_; _K. cristata_, 8, 29, 32, 66, +81+, +109+, 148, +149+ Lacunæ--air-spaces, 70, 73 _Lagurus_--Hare’s-tail, 76, 88, 90, 92, 100, 101, 109; _L. ovatus_, 31 Lamina--the blade of the leaf, 63-71, 95 Lanceolate--narrow and tapering at both ends, 163 Lanceolate-acuminate--lanceolate, but the upper end drawn out to a long point, 163 Large grasses, 6 Lawns, 10, 37 Lax--loose, the spikelets on slender branches some distance apart, 110, 117 Layed shoots, 15 Leaf, +17+-+27+, 39-61, 95, 133 Leaf anatomy, 62-71, 72-82 Leaf-apex, +21+ Leaf-base, 10, 22, 40 Leaf-blade--Lamina Leaf characters, 4, +20+-+27+ Leaf-margin, +22+, 44, 66 Leaf-section, _16_, 20, +62+-+72+ Leaf-stalk--Petiole Leaf-surface, +22+, 65, 66, 67 Least Quaking-grass--_Briza minor_ Leathery leaves, 21 _Leersia_--Cut-grass, 67, 70, 77, 90, 91, 92, 105, 120; _L. oryzoides_, 30, 66, 137 Leguminosæ, 3 _Lepturus_, 87, 90, 99; _L. filiformis_--_L. incurvatus_; _L. incurvatus_, 31 Ligule, _18_, _19_, 45, 46, 51, 95, 113, 133 Limestone species, 32 Linear--at least five times as long as broad, with parallel straight sides, 19 Linear-acuminate--linear, but tapering to a long point at the apex, 19 Linear-acute--linear, but pointed at the apex, 39 Linear-lanceolate--linear, but tapering at both ends, 19, 20, 163, 168 Linear-oblong--oblong, but drawn out so that the sides are parallel for some distance, 16 Local grasses, 30, 31