Grasses

CHAPTER I.. The Vegetative Organs.

THE VEGETATIVE ORGANS.

That grasses are interesting and important plants is a fact recognised by botanists all the world over, yet it would appear that people in general can hardly have appreciated either their interest or their importance seeing how few popular works have been published concerning their structure and properties.

Apart from their almost universal distribution, and quite apart from the fascinating interest attaching to those extraordinary tropical giants, the Bamboos, West Indian Sugar-cane, the huge Reed-grasses of Africa, the Pampas-grasses of South America; and from the utilitarian value of the cereals--Maize, Rice, Wheat and other corn, &c.--everyone must be struck by the significance of the enormous tracts of land covered by grasses in all parts of the world, the Prairies of North America and the Savannahs of the South, the Steppes of Russia and Siberia, and the extensive tracts of meadow and pasture-land in Europe being but a few examples.

Although in the actual number of species the Grass family is by no means the largest in the vegetable kingdom, for there are far more Composites or Orchids, the curious sign of success in the struggle for existence comes out in grasses in that the number of individuals far transcends those of any other group, and that they have taken possession of all parts of the earth’s surface. Some species are cosmopolitan--e.g. our common Reed, Arundo Phragmites; while others--e.g. several of our native species of Festuca and Poa--are equally common in both hemispheres. On the whole the Tropics afford most species and fewest individuals, and the temperate regions most individuals.

Considering their multifarious uses as fodder and food, for brewing, weaving, building and a thousand other purposes, it is perhaps not too much to say that if every other species of plant were displaced by grasses of all kinds--as many indeed gradually are--man would still be able to supply his chief needs from them.

The profound significance of the grass-carpet of the earth, however, comes out most clearly when we realise the enormous amounts of energy daily stored up in the countless myriads of green blades as they fix their carbon. By decomposing the carbon-dioxide of the air in their chlorophyll apparatus by the action of the radiant energy of the sun, they build up starches and sugars and other plant-substances, which are then consumed and turned into flesh by our cattle and sheep and other herbivorous animals, and so furnish us with food. The whole theory of agriculture turns on this pivot, and the by no means small modicum of truth in such sayings as “All flesh is grass,” and that the man who can make two blades of grass grow where one grew before deserves well of his country, obtains a larger significance when it is realised that the only real gain of wealth is that represented by the storage of energy from without which comes to us by the action of green leaves waving in the sunshine.

The true Grasses, comprising the Natural Order Graminaceæ--also written Gramineæ--are often popularly confounded with other herbs which possess narrow green ribbon-like leaves, or even with plants of very different aspects--e.g. Cotton-grass (Eriophorum) and other Sedges, and the names Rib-grass (Plantago), Knot-grass (Polygonum), Scorpion-grass (Myosotis) and Sea-grass (Zostera), as well as the general usage of the word grass to signify all kinds of leguminous and other hay-plants in agriculture, point to the wider use of the word in former times. This has been explained by the use of the words gaers, gres, gyrs, and grass in the old herbals to indicate any kind of small herbage.

In view of the importance of our British grasses in agriculture, I have here put together some results of observation and reading in the hope that they may aid students in recognising easily our ordinary agricultural and wild grasses. During several years of work in the fields, principally directed at first to the study of the parasitic fungi on grasses, and subsequently to that of the importance of grasses in forestry and agriculture, and to the variations they exhibit, the need of some guide to the identification of a grass at any time of the year, whether in flower or not, forced itself on the attention, and although a botanist naturally turns to a good Flora when he has the grass in flower, as the best and quickest way of ascertaining the species, it soon became evident that much may be done by the study of the leaves and vegetative parts of most grasses. Indeed some are recognisable at a glance by certain characters well known to continental observers: in the case of others the matter is more difficult, and perhaps with a few it is impossible to be certain of the species from such characters only.

Nevertheless, while the best means for the determination of species are always in the floral characters so well worked up in the Floras of Hooker, Bentham and others, there is unquestionably much value in the characters of the vegetative organs also, as the works of Jessen, Lund, Stebler, Vesque and others abroad, and Sinclair, Parnell, Sowerby and others in this country attest.

Almost the only plants confounded with true grasses by the ordinary observer are the sedges and a few rushes. Apart from the very different floral structures, there are two or three easily discoverable marks for distinguishing all our grasses from other plants (Fig. 1). The first is their leaves are arranged in two rows, alternately, up the stems; and the second that their stems are circular or flattened in section, or if of some other shape they are never triangular and solid (Figs. 6 and 7). Moreover the leaves are always of some elongated shape, and without leaf-stalks, but pass below into a sheath, which runs some way down the stem and is nearly always perceptibly split (Figs. 8-13). Further, the stems themselves are usually terete, and distinctly hollow except at the swollen nodes, and only branch low down at the surface of the ground or below it.

All our native grasses are herbaceous, and none of them attain very large dimensions. In the following lists I term those small which average about 6-18 inches in the height of the tufts, whereas those over 3 feet high may be termed large, the tufts being regarded as in flower. The sizes cannot be given very accurately, and starved specimens are frequently found dwarfed, but in most cases these averages are not far wrong for the species freely growing as ordinarily met with, and in some cases are useful. I have omitted the rare species throughout, and in the annexed lists have added the popular names.

LARGE GRASSES.

(Over 3 feet.)

Milium effusum (Millet-grass). Digraphis arundinacea (Reed-grass). Aira cæspitosa (Tufted Hair-grass). Arrhenatherum avenaceum (False Oat). Elymus arenarius (Lyme-grass). Bromus asper (Hairy Brome). B. giganteus (Tall Brome). Festuca elatior (Meadow Fescue). F. sylvatica (Reed Fescue). Glyceria aquatica (Reed Sweet-grass). G. fluitans (Floating Sweet-grass). Arundo Phragmites (Common Reed).

MEDIUM GRASSES.

(1-3 feet.)

Phleum pratense (Timothy). Avena pratensis (Perennial Oat-grass). Anthoxanthum odoratum (Sweet Vernal). Alopecurus agrestis (Slender Foxtail). A. pratensis (Meadow Foxtail). Agrostis alba (Fiorin). Psamma arenaria (Sea Mat-grass). Avena flavescens (Yellow Oat-grass). Holcus lanatus (Yorkshire Fog). Hordeum sylvaticum (Wood Barley). H. pratense (Meadow Barley). Agropyrum repens (Couch-grass). A. caninum (Fibrous Twitch). Lolium italicum (Italian Rye-grass). Brachypodium sylvaticum (Wood False-Brome). B. pinnatum (Heath False-Brome). Bromus erectus (Upright Brome). B. sterilis (Barren Brome). B. arvensis (Field Brome). Festuca ovina (var. rubra, &c.). (Sheep’s Fescue). F. elatior (var. pratensis). (Meadow Fescue.) Dactylis glomerata (Cock’s-foot). Cynosurus cristatus (Crested Dog’s-tail). Poa pratensis (Meadow-grass). P. trivialis (Rough stalked Meadow-grass). P. nemoralis (Wood Poa). Molinia cærulea (Flying Bent). Melica nutans (Mountain Melick). M. uniflora (Wood Melick).

SMALL GRASSES.

(6-18 inches.)

Phleum arenarium (Sand Cat’s-tail). Alopecurus geniculatus (Marsh Foxtail). Agrostis canina (Brown Bent). Aira flexuosa (Wavy Hair-grass). Aira canescens (Grey Hair-grass). A. præcox (Early Hair-grass). A. caryophyllea (Silvery Hair-grass). Nardus stricta (Moor Mat-grass). Hordeum murinum (Wall Barley). H. maritimum (Sea Barley). Lolium perenne (Rye-grass). L. temulentum (Darnel). Bromus arvensis (var. mollis). (Field Brome). Festuca ovina (Sheep’s Fescue). F. Myuros (Rat’s-tail Fescue). Briza media (Quaking-grass). Poa maritima (Sea Poa). P. annua (Annual Meadow-grass). P. compressa (Flattened Meadow-grass). P. alpina (Alpine Poa). P. bulbosa (Bulbous Poa). Triodia decumbens (Heath-grass). Kœleria cristata (Crested Kœleria).

The roots of our grasses are almost always thin and fibrous and are adventitious from the nodes, frequently forming radiating crowns round the base and easily pulled up, and usually broken in the process; but in the case of a few moor grasses--especially Nardus (Fig. 2) and Molinia--the roots are so tough and thick (stringy) as to resist breakage very efficiently. In stoloniferous grasses a similar difficulty of removal may be caused in a slighter degree by the underground stems. In a few cases, e.g. Alopecurus bulbosus (Fig. 3), Poa bulbosa, Phleum pratense and P. Bœhmeri, Arrhenatherum avenaceum, and to a slighter extent in Poa alpina and one or two others, the lowermost internodes and sheaths of the stems may be swollen and stored with food-materials, and a sort of tuber or bulb results; this is especially apt to occur in dry sandy soils. In old lawns, pastures, &c., the roots of Poa annua and others may have nodules on them due to the presence of certain small Nematode worms, Heterodera.

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