In most grasses the blades are _convolute_--i.e. rolled up like the paper of a cigarette, one edge over the other--and the section of the shoot is round (Fig. 7). In some cases, however, the leaves are _conduplicate_--i.e. each half of the lamina is folded flat on the other, the upper sides being turned face to face inwards, with the mid-rib as the hinge--and in this case the shoots are more or less compressed (Fig. 6). [Illustration: Fig. 6. _Dactylis glomerata._ Transverse section of a leaf-shoot (× 5). _A_, conduplicate leaf-blade. _B_, sheath. Stebler.] [Illustration: Fig. 7. _Digraphis arundinacea._ Transverse section of a leaf-shoot (× 5). _A_, sheath. _B_, convolute leaves. Compare Fig. 14. Stebler.] In these latter cases the transverse section may be elliptical--e.g. _Poa pratensis_ and _P. alpina_, _Briza_, &c., or more flattened and linear-oblong--e.g. _Glyceria fluitans_--with the flattened sides straight, or the section is oval but pointed more or less at each end owing to projecting keels and leaf-edges, and the form is _naviculate_--e.g. _Glyceria aquatica_, _Dactylis_ (Fig. 6)--or, the sides being less flattened, more or less _rhomboidal_ as in _Poa trivialis_. In _Melica_ the leaves are convolute and the shoot-section _quadrangular_. Flat, and usually sharp-edged shoots. _Dactylis glomerata_ (Fig. 6). _Poa trivialis_, _P. annua_, _P. pratensis_, _P. compressa_, _P. maritima_, and _P. alpina_. _Glyceria aquatica_ and _G. fluitans_. _Avena pubescens._ _Lolium perenne._ CHAPTER II. THE VEGETATIVE ORGANS (_continued_). The leaves of all our grasses consist of the _blade_, which passes directly into the _sheath_, without any petiole or leaf-stalk (Fig. 1). The sheath is usually obviously _split_, and so rolled round the internode that one edge overlaps the other, but in the following grasses the sheath is either quite _entire_, or only slit a short way down, the two edges being fused as it were for the greater part of its length. Sheath more or less entire. _Glyceria aquatica_ and _G. fluitans_. _Melica uniflora_ and _M. nutans_. _Dactylis glomerata._ _Poa trivialis_ (Fig. 8), _P. pratensis_, _P. alpina_. _Sesleria cærulea._ _Bromus_ (all the species). _Briza media_ and _B. minor_. In some cases--e.g. _Arrhenatherum_, _Bromus asper_, and _Holcus lanatus_--the sheath is marked with a more or less prominent ridge down its back, due to the continuation of the _keel_ of the leaf. The sheath may also be glabrous or hairy, and grooved or not. A few grasses are so apt to develope characteristic colours in their sheaths, especially below, that they may often be recognised in winter by this peculiarity. Sheaths coloured. _Lolium_--all red. _Holcus_--red with purple veins. _Festuca elatior_--red. _Cynosurus_--yellow. _Alopecurus pratensis_, and _A. agrestis_--violet-brown, &c. _Festuca ovina_, var. _rubra_--red.