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Read Ebook: Grasses: A Handbook for use in the Field and Laboratory by Ward H Marshall Harry Marshall
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Ebook has 745 lines and 54403 words, and 15 pages
THE VEGETATIVE ORGANS 1
THE VEGETATIVE ORGANS 17
GRASSES CLASSIFIED ACCORDING TO THEIR VEGETATIVE CHARACTERS 39
ANATOMY AND HISTOLOGY 62
GRASSES CLASSIFIED ACCORDING TO THE ANATOMICAL CHARACTERS OF THE LEAF 72
GRASSES IN FLOWER 83
GRASSES GROUPED ACCORDING TO THEIR FLOWERS AND INFLORESCENCES 99
THE FRUIT AND SEED 119
CLASSIFICATION OF GRASSES BY THE "SEEDS" 135
BIBLIOGRAPHY 175
INDEX, GLOSSARY AND LIST OF SYNONYMS 177
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.
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.
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.
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.
MEDIUM GRASSES.
SMALL GRASSES.
ANNUALS.
ANNUALS
which may become biennial or perennial.
PERENNIALS.
With intra-vaginal branches only.
With extra-vaginal shoots.
Creeping below ground and truly stoloniferous.
Tufted Grasses.
Creeping above ground .
A point of considerable classificatory value is the shape of the transverse section of the shoot, which is correlated with the mode of folding up of the young leaf-blades.
Flat, and usually sharp-edged shoots.
THE VEGETATIVE ORGANS .
Sheath more or less entire.
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.
The leaf-blade is long or short, broad or narrow, but always of some elongated form such as linear, linear-lanceolate or linear-acuminate, or subulate, setaceous, &c., varying as to the degree of acuteness of the apex, and the tapering of the base.
As we shall see later the degree of inrolling of many grass leaves varies with circumstances.
Further characters of the leaves are derived from their texture, apex, margins, mid-ribs and venation, hairiness, and especially the presence and characters of the longitudinal ridges which run along the upper or lower surface in many cases.
A very interesting anatomical adaptation is met with in the leaves of many grasses which grow in dry situations such as on sandy sea-shores, exposed mountains and so forth. When the air is moist, in wet weather or in the dews, and the sun's rays not too powerful, the leaf is spread out with its upper surface flat or nearly so, but when the scorching sun and dry air or winds prevail, the leaves fold or roll up, with the upper sides apposed or overlapping inside the hollow cylinder thus made.
In such leaves some of the upper epidermal cells, either next the mid-rib or between the other ribs are large and very thin-walled, full of sap when distended, and so placed that as they lose water by evaporation they contract, and so draw together the two halves of the lamina or each ribbed segment , thus causing the infolding or inrolling . Not only from the structure and actions of these motor-cells, but also from the fact that the stomata are on the upper surfaces and thus protected, and that the lower surfaces which alone are exposed to the drought are defended by hard and impenetrable tissues, we must look upon these as adaptations to the xerophytic conditions.
Leaves prominently ridged.
Leaves practically devoid of ridges.
In some grasses the tissue over the mid-rib is considerably raised and strengthened on the dorsal side of the blade as a "keel."
Keel more or less prominent.
HAIRY GRASSES.
To a less extent.
The habitat of grasses is of great importance as an aid to determination. No one would expect to find a sea-shore grass growing in a beech-forest, or an aquatic grass on a dry chalk-down; but they are even more true to their habitats than this, and I append the following lists of habitats of British grasses as of use in determining them, though it is not pretended that the limits are absolute.
In the following list "pasture-grass" means useful for grazing, and "meadow-grass" one that is especially valuable for mowing--i.e. for hay. A "weed" is used in its agricultural sense for a grass not useful and not wanted on cultivated land, though often found there.
MEADOW-AND PASTURE-GRASSES.
SHADE-GRASSES.
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