A Text-book of botanyMacmillan, 1898 - 632 pàgines |
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Frases i termes més freqüents
Algae androecium antheridia anthers apex apical archegonia asexual assimilation axis bast become bodies bordered pits branches buds cambium capsule carbonic acid carpels cavities cell walls chlorophyll chromatophores colour consists contain corolla curvature cytoplasm Dicotyledons division egg-cell elongated embryo epidermis exhibit external female fertilisation fibres filaments flowers formation frequently fructifications fruit fundamental tissue Fungi genus geotropic germination give rise green growing point growth heliotropic hyphæ inflorescences layer leaf leaves living longitudinal medullary rays movements nucleus nutritive occur OFFICINAL organs outer ovary ovules oxygen parenchyma perianth perigone Phanerogams phloem plants pollen portions position produced protoplasm reproduction result rhizomes roots seeds sexual shoots side sieve-tubes species spermatozoids sporangia sporangium spores stalk stamens starch grains stem stomata strands structure substances surface swarm-spores tendrils thallus thickened tion tracheids transpiration transverse trees tropical tubers usually vascular bundles vegetative cone whorls wood woody xylem zygomorphic
Passatges populars
Pàgina 46 - A highly organized plant which begins its development with the simplest stages and gradually advances to a higher state of differentiation repeats in its ontogeny itsphylogenetic development " ; and further on, " From the fossil remains of former geological periods it is safe to conclude that such Conifers as Thuja, Biota, and the various Junipers that now have scalelike compressed leaves have been derived from Conifers with needle-shaped leaves. This conclusion is further confirmed by the fact...
Pàgina 217 - BY PLANTS. WHILE IN THE PROCESS OF ASSIMILATION GREEN PLANTS ALONE, AND ONLY IN THE LIGHT, DECOMPOSE CARBONIC ACID AND GIVE OFF OXYGEN, ALL PLANT ORGANS WITHOUT EXCEPTION BOTH BY DAY AND BY NIGHT TAKE UP OXYGEN AND GIVE OFF CARBONIC ACID. Organic substance, obtained by assimilation, is in turn lost by respiration.
Pàgina 51 - ... tubercles, that is to say, small rounded bodies, visible to the naked eye. The bacilli, lodged in these tubercles of which they cause the formation, are parasites, belonging to the lowest scale of vegetable life and must be considered as the specific cause of all tuberculous diseases. This parasite, so small that it can only be seen with the aid of a powerful microscope, not only gradually destroys the lung substance through ulcerative processes, but at the same time gives off certain poisonous...
Pàgina 375 - ... intimate connection, and together forming a compound thallus or CONSORTIUM. Strictly speaking, both Fungi and Algae should be classified in their respective orders; but the Lichens exhibit among themselves such an agreement in their structure and mode of life, and have been so evolved as consortia, that it is more convenient to treat them as a separate class. In the formation of the thallus the algal cells become enveloped by the mycelium of the fungus in a felted tissue of hyphae (Fig.
Pàgina 375 - The Fungus derives its nourishment saprophytically from the organic matter produced by the assimilating Alga, without at the same time behaving as a parasite and injuriously interfering with its vegetative activity.
Pàgina 47 - Eeference is also made to the Australian Acacias, whose early pinnate leaves in many cases become eventually phyllodes, and he concludes with these words : " That it is permissible on such phylogenetic grounds to conclude that the Australian Acacias have lost their leaf-blades in comparatively recent times, and have in their stead developed the much more resistant phyllodes as being better adapted to withstand the Australian climate. The appearance accordingly of the phyllodes at so late a stage...
Pàgina 75 - The different colors of flowers are due to the varying color of the cell-sap, to the different distribution of the cells containing the colored cell-sap, and also to the combinations of dissolved coloring matter with the yellow, orange, and red chromoplasts and the green chloroplasts. There is occasionally found in the cell-sap a yellow coloring matter known as xanthein; it is nearly related to xanthophyll, but soluble in water.
Pàgina 72 - Crystals of Calcium Oxalate. — Few plants are devoid of such crystals. They are formed in the cytoplasm, within vacuoles which afterwards enlarge and sometimes almost fill the whole cell. In such cases the other components of the cell become greatly reduced ; the cell walls at the same time often become corky, and the whole cell becomes merely a repository for the crystal. The crystals may be developed singly in a cell, in which case they are of...
Pàgina 74 - ... sap of a number of deeply colored parts of plants in a crystalline or amorphous form. Blood-colored leaves, such as those of the copper beech, owe their characteristic appearance to the united presence of green chlorophyll and anthocyanin. The different colors of flowers are due to the varying color of the cell sap, to the different distribution of the cells containing the colored cell sap, and also to the combinations of dissolved coloring matter with the yellow, orange, and red chromoplasts...
Pàgina 458 - FRUIT). Such inflorescences are wanting or ill developed among the Gymnosperms, while in the Angiosperms they are often well differentiated, constituting unities of a higher order. The modifications exhibited by the fertile shoots of such an inflorescence are due, partly to a difference in their mode of branching, partly to the reduction or the metamorphosis of their leaves. These changes are the result of an adaption to pollination, in the endeavor to aggregate and at the same time render the flowers...