« PredošláPokračovať »
Sub-class I. THALAMIFLORÆ.—Flowers usually with calyx and
corolla, petals separate, inserted on the thalamus or receptacle, and stamens hypogynous (below ovary), as in Fig. 21, p. 222.
Example—buttercup and wallflower. Sub-class II. CALYCIFLORÆ.— Flowers usually with calyx and
corolla, petals either separate or united, stamens either
Fig. 23, p. 224.
strawberry, and hemlock.
ample—harebell and dandelion.
Sub-class III. COROLLIFLORÆ.—Flowers usually having calyx and
corolla, petals united, corolla hypogynous (below ovary). Ex
ample—foxglove and primrose. Sub-class IV. MONOCHLAMYDEA or A PETALÆ.-Flowers either
with calyx only, or without any envelope. Section 1. Angiospermo.-Seeds contained in a seed-vessel, and
ovules fertilized by the action of the pollen on the stigma.
Example-pellitory and willow.
by direct action of the pollen upon them, without the in-
Class II.- MONOCOTYLEDONES or ENDOGENÆ, in which
spiral vessels are present; the stem is endogenous ; venation of leaves parallel ; flowers with ternary symmetry ; embryo
monocotyledonous. Sub-class I. PETALOIDEÆ.—Flowers consisting of a coloured peri
anth (calyx and corolla) or of whorled scales.
Example—narcissus and snowdrop.
E.cample-tulip and lily.
lying like tiles on a house) glumes or bracts. Ex.-grasses.
B. CRYPTOGAMOUS OR FLOWERLESS PLANTS, WITHOUT COTYLEDONS,
AND WITH NO TRUE STAMENS NOR PISTILS.
Class III. ACOTYLEDONES, plants either cellular or having
scalariform vessels (tubes marked with lines or bars so as to be like steps of a ladder); stem when woody is acrogenous ; leaves veinless or with forked venation ; reproductive organs peculiar
cellular bodies or spores ; no cotyledons. Sub-class I. ACROGENÆ.—Having a distinct leafy stem, with
scalariform vessels. Example-ferns and mosses. Sub-class II. THALLOGENÆ.—Having no distinct stem nor leaves,
but forming a cellular expansion or thallus without vessels.
Example-lichens and seaweeds. Under these classes and sub-classes are included numerous orders, the names of which are usually derived from some typical genus.
The more deeply we study the structure of plants, and the more diligently we compare those belonging to different countries, the more likely are we to arrive at correct views relative to vegetable groups.
Great advances have been made in arrangement, but we cannot say that botanists have yet agreed as to the true system of nature. In attempting to ascertain it we must take a comprehensive view of all the plants of the world, and we must know accurately the structure of their organs in all its diversity. The highest powers of mind may thus be engaged in tracing out the handiwork of Him who is wonderful in counsel and excellent in working. Methodical arrangement is conspicuous in God's works. He is a God of order. His plan is perfect, although we may not have attained to the knowledge of it. The discoveries of science are daily adding new means for the attainment of this knowledge, and we may hope for the final development of the plan of the almighty Architect.
DISTRIBUTION OF PLANTS.
Wherever circumstances are compatible with vegetable existence, there we find plants arise. The solitary island in the midst of the ocean, as well as the extended continent ; the parched desert, and the fertile plain ; the deep cavern, and the lofty mountain ; the stagnant pool, and the meandering stream, have each their
peculiar vegetation. Even the sides of the volcano are covered with flowers ; and the geysers of Iceland, and the hot springs of Switzerland and Arabia, are not without their vegetable productions. The ever-sounding and mysterious deep hides in its bosom many a plant no less conspicuous for beauty and variety of form than splendour of colour, and admirably fitted for the place it is designed to occupy.
On the sands of the torrid zone, the eye of the traveller is occasionally refreshed by the appearance of a few succulent plants which are enabled to thrive amidst these arid regions ; and in the realms of perpetual snow which surround the poles, attention is arrested by the prospect of fields of red snow, which owe their existence in part to plants of a microscopic nature (Protococcus nivalis). Thus it is that vegetation is spread over all quarters of the globe, and is wisely adapted to all varieties of climate.
“ The carpet of flowers and of verdure,” Humboldt remarks, “ spread over the naked crust of our planet, is unequally woven ; it is thicker where the sun rises high in the ever-cloudless heavens, and thinner towards the poles—in the less happy climes where returning frosts often destroy the opening buds of spring, or the ripening fruits of autumn. Everywhere, however, man finds some plants to minister to his support and enjoyment.” “ Those who view nature with a comprehensive glance,” he continues,“ see, from the poles to the equator, organic life and vigour gradually augment with the augmentation of vivifying heat. But in the course of this progressive increase, there are reserved to each zone its own peculiar beauties: to the tropics, variety and grandeur of vegetable forms; to the north, the aspect of its meadows and green pastures, and the periodic awakening of nature at the first breath of the mild air of spring. Each zone, besides its own peculiar advantages, has its own distinctive character - each region of the earth has a natural physiognomy peculiar to itself. The idea indicated by the painter, by expressions such as Swiss nature, Italian sky, &c., rests on a partial perception of this local character in the aspect of nature. The azure of the sky, the lights and shadows, the haze resting in the distance, the form of animals, the succulency of the plants and herbage, the brightness of the foliage, the outline of the mountains, are all elements which determine the total impression characteristic of each district or region.”
Dr. W. H. Campbell, in giving an account of the vegetation of the forests of Demerara, writes :- “ The luxuriance of the vegetation surpassed everything you could conceive. Every inch of ground was occupied, and the eye looked in vain for any spot which nature had left unclothed and less bountifully supplied than that immediately around you. Indeed, it seemed as if there was one dire scramble for existence, and that each was striving with might and main to reach the upper light and air, lest being left behind in the race, the forfeiture of life should be the penalty."
As we proceed from warm regions towards the poles, we find that as the light and heat diminish, vegetation is checked in the same proportion. . At every step of our progress we change the vegetable group.
From the hottest climates we pass in succession through those of the pine-apple, sugar-cane, coffee, date, cotton, citron, and olive, till we reach the region of the vine. The spices and fruits of equatorial Asia are succeeded, in th thickets to the east of the Caspian, by the apricot, the peach, and the walnut. In the southern regions of Europe, the dwarf palm, the cypress, and the cork tree make their appearance ; the orange and lemon perfume the air with their blossoms, and the myrtle and pomegranate grow wild among the rocks. Again, when we pass the Alps, we find the vegetation of northern climates ; forests of oak, beech, and elm adorn the landscape, and are ultimately replaced by various species of hazel, fir, and birch.
The vegetation of cold regions does not assume any of the grandeur and luxúriance which we observe in the tropics. As we approach the shores of the arctic ocean, the trees become few and diminutive. In Siberia, their thin and distorted trunks are clad, as it were, with a fur-like covering of lichens, which occupy the place of the orchids of warm regions. Farther north, the only shrub we find is the dwarf birch ; and a little beyond the 70th degree not a tree or shrub is to be seen. Spitzbergen is said to produce only one plant possessed of a proper woody stem ; mosses form more than a quarter of the whole vegetation of Melville Island, and the soil of New South Shetland is covered with specks of mosses struggling for existence. Dr. Hooker states that on one of the antarctic islands he gathered the ghosts of eighteen cryptogamic plants, chiefly mosses and lichens; and that there appeared no trace whatever of flowering plants. Even in those regions where snow lies upon the ground during the greater part of the year, the Creator calls into existence peculiar tribes of plants, which are enabled, during the short summer of such inhospitable climes, to pass through their various periods of sprouting, flowering, and fruiting. The plants, so to speak, seem to fear lest they should not be able to perfect their seeds before the cold and darkness arrest their growth.
The adaptation of plants to different climates is a subject well fitted to call forth our admiration. The succulent plant, well provided with stores of fluid, and in which evaporation takes place with the greatest difficulty, is made to grow in the parched and thirsty district. In the deserts of the East, and the sandy plains of Arabia, where the heat from the earth dissipates the passing cloud, which hastens, as it were, to shed its refreshing moisture on a more grateful spot, where no water issues from a spring or falls from on high, there the water-melon grows, offering a delicious draught to the traveller. On the pampas of South America, the Cactus, with its juicy stems, like a vegetable fountain, refreshes the wild herds which roam over the plains, and which instinctively tear off the formidable external prickles of the plant in order that they may reach the succulent interior. The Ravenala, or traveller's tree, furnishes from the base of its leaves a supply of water to the traveller in Madagascar. The palm develops its umbrageous foliage in those regions where it is most required for shelter from the heat of the sun. The bread-fruit, banana, plantain, mango, and coco-nut, are produced in abundance in those climates where they are best fitted for the support and wellbeing of the inhabitants. In temperate climes, where animal food is more essential to existence, we meet with the grassy herbage and the green pastures adapted for the food of cattle ; while in arctic regions, the lichen on which the rein-deer feeds, thrives at a temperature sufficient to kill most other plants.
J. H. BALFOUR.