proof of biennial character is not always easy, however, and a few grasses may be either annual or biennial, or biennial or perennial, according to conditions—e.g. species of Hordeum, Bromus, &c. In the following lists I have given the duration of the principal grasses, where the character is especially important.

Annuals.

Phleum arenarium. Aira præcox. A. caryophyllea. Hordeum murinum. H. maritimum.

Lolium temulentum. Festuca Myurus. Briza minor. Poa rigida. P. annua.

Annuals

which may become biennial or perennial.

Alopecurus geniculatus. Hordeum pratense. Lolium perenne. L. italicum (may be perennial). Bromus asper (may be perennial). B. sterilis. B. arvensis (may be perennial).

Perennials.

Holcus lanatus. H. mollis. Nardus. Hordeum sylvaticum. Agropyrum. Brachypodium. Bromus erectus. B. giganteus. Festuca ovina. F. elatior. F. sylvatica. Dactylis. Cynosurus cristatus. Briza media. Milium. Anthoxanthum. Digraphis. Phleum pratense. Alopecurus pratensis. Agrostis alba. A. canina.

Psamma. Aira cæspitosa. A. flexuosa. A. canescens. Avena pratensis. A. flavescens. Arrhenatherum. Glyceria aquatica. G. fluitans. Poa maritima. P. compressa. P. pratensis. P. trivialis. P. nemoralis. P. alpina. P. bulbosa. Molinia. Melica. Triodia. Kœleria. Arundo.

Fig. 4. Catabrosa aquatica. Plant showing the creeping habit, rooting nodes, and paniculate inflorescence (reduced). Parnell.

The rhizome of a perennial grass is continued sympodially by means of buds branching from the lowermost joints of the flowering shoots, and some importance is attached to the mode of spreading of these lateral sprouting shoots. The buds always arise in the axils of the lower leaf-sheaths—i.e. they are intra-vaginal. If they remain intra-vaginal during further growth, the shoots are forced upwards and only tufts (Fig. 2) are formed, except in so far as such shoots may fall prostrate on the surface of the ground later, and throw out roots from their nodes, and so act as runners or offsets, or put out a few roots &c. as they ascend through the soil. But in many cases the buds soon burst through the leaf-sheaths, and develope as extra-vaginal shoots, and may then run horizontally as underground stolons. Only creeping grasses of these latter kinds can rapidly cover large areas4: the grasses with intra-vaginal shoots only can only make tufts or "tussocks." Several peculiarities in the habits of grasses depend on these facts. The following are the most important creeping, or stoloniferous species, contrasted with the much more common tufted and the far rarer grasses with runners above ground (Fig. 4). Some of these (Elymus, Psamma, &c.) are of great importance as sand-binders.

With intra-vaginal branches only.

Lolium—slightly stoloniferous. Festuca elatior—slightly stoloniferous. Avena flavescens—slightly stoloniferous. Phleum pratense—no stolons, but may be bulbous. Dactylis—no stolons. Festuca ovina—no stolons. Poa alpina—no stolons. Cynosurus—no stolons.

With extra-vaginal shoots.

Arrhenatherum—short stolons, sometimes bulbous. Holcus lanatus—creeping. Alopecurus pratensis—long stolons. Anthoxanthum—slightly stoloniferous. Agrostis alba (var. stolonifera)—long stolons and runners. Digraphis—long stolons. Poa pratensis—long stolons. P. trivialis—runners only. Festuca heterophylla, Lam.—a variety of F. ovina with slight stolons. F. rubra (Linn.)—a variety of F. ovina with long stolons. Bromus erectus—no stolons. B. inermis—long stolons.

Creeping below ground and truly stoloniferous.

Agropyrum. Elymus. Psamma. Poa pratensis. P. compressa. Agrostis alba (var. stolonifera). Alopecurus pratensis. Brachypodium (slightly).

Bromus erectus (slightly). Festuca ovina (var. rubra, Linn.). F. elatior (slightly). Briza (slightly). Glyceria. Poa maritima. Melica. Arundo.

Tufted Grasses.

Milium. Agrostis alba (on downs, &c.). Aira cæspitosa. A. flexuosa. A. canescens. A. præcox. A. caryophyllea. Avena pratensis (slightly creeping). Arrhenatherum. Nardus (Fig. 2). Hordeum sylvaticum. Lolium. Bromus. Festuca ovina (except some varieties).

F. sylvatica. F. Myurus. Dactylis. Cynosurus. Poa rigida. P. annua. P. trivialis. P. nemoralis. P. alpina. P. bulbosa. Molinia. Triodia. Kœleria.

Creeping above ground (with runners).

Holcus lanatus.