Different stages in the formation and germination of the zygospore.
The conditions for germination are much the same as for growth in general.
Further, the older the seed the more slow as a general rule will germination be in starting, but there are notable exceptions.
A spirit has been distilled from acorns in process of germination, when the saccharine principle is most abundant.
The mesodermic portion becomes charged with a yolk-like material (y), and, on the germination of the statoblast, gives rise to the outer layer (mes) of the bud.
The oospore on germination usually gives origin A ?°.
The time required for germination in the most favourable circumstances varies very greatly, even in the same species, and in seeds taken from one pod.
While the spore of Bryophyta on germination gives rise to the sexual plant, the carpospore of the alga may give rise on germination to a plant bearing a second sort of asexual cells, viz.
This peculiar product of germination, which intervenes between the oospore and the adult form, is the proembryo.
The viscid pulp soon hardens, affording a protection to the seed; in germination the sucker-root penetrates the bark, and a connexion is established with the vascular tissue of the first plant.
On germination of the seed the radicle first grows out, increasing in size as a whole, and soon adding to its tissues by cell division at its apical growing-point.
Tophthora infestans passing K, Germination of the zoospores through the stomata D, on formed in the sporangia.
34 (1900); Bernard, "On some Different Cases of Germination," Gardener's Chronicle (1900); Pierce, Publ.
13, - A series of phases of germination of the spore of B.
(2) The Procharisteria at the end of winter, at which thanks were offered for the germination of the seed.
On germination, however, the fungus behaves in the same way as one which has entered in the seedling stage.
Miss Nichols fi -ids that it occurs very soon after the germination of the spore in Cc sinus, but no fusion of cells or migration of nuclei was to be observed.
On germination it gives rise to a row of cells in which short (nodal) and long (internodal) cells alternate.
This pause, often of so long duration, in the growth of the embryo between the time of its perfect development within the seed and the moment of germination, is one of the remarkable and distinctive features of the life of Spermatophytes.
The aim of germination is the fixing of the embryo in the soil, effected usually by means of the root, which is the first part of the embryo to appear, in preparation for the elongation of the epicotyledonary portion of the shoot, and there is infinite variety in the details of the process.
The germination of the spores has now been observed in several forms with care.
In Zygnemaceae and Mesocarpaceae the zygospore, after a period of rest, germinates, to form a new filamentous colony; in Desmidiaceae its contents divide on germination, and thus give rise to two or more Desmids.
When zoospores come to rest, a new cell is formed and germination ensues at once.
To take an example, Lemanea and Batrachospermum are Florideae which bear densely-whorled branches, but which, on the germination of the carpospore, give rise to a laxly-filamentous, somewhat irregularly-branched plant, from which the ordinary sexual plants arise at a later stage.
A The spores are capable of germination at once, or they may be kept for months and even years, and are very resistant against desiccation, heat and cold, &c. In a suitable medium and at a proper temperature the germination is completed in a few hours.
(After de Bary.) "1, fragments of filaments with ripe spores; 2-5, successive stages in the germination of the spores, the remains of the spore attached to the germinal rodlets.
Every plant is constrained to carry Out its functions of germination, growth, nutrition, reproduction, &c., between certain limits of temperature, and somewhere between the extremes of these limits each function finds ao optimum temperature at which the working of the living machinery is at its best, and, other things being equal, any great departure from this may induce pathological conditions; and many disasters are due to the failure to provide such suitable temperaturese.g.
The rows of cells from which the laticiferous vessels are formed can be distinguished in many cases in the young embryo while still in the dry seed (Scott), but the latex vessels in process of formation are more easily seen when germination has begun.
The tuft of hairs at the base facilitates rapid dispersion of the seed, early germination of which is rendered desirable owing to its tenuity.
Experimental farms and various effective organiza tons for assisting the live-stock, dairying and fruitgrowing industries, for testing the germination and purity of agricultural seeds, and for developing the export trade in agricultural and dairy produce.
Seeds are tested in the laboratory for purity and germination on behalf of farmers and seed merchants, and scientific investigations relating to seeds are conducted and reported upon.
Germination is often slower where there is a store of available food in the perisperm, or in the endosperm, or in the embryo itself, than where this is scanty or wanting.
Exalbuminous Dicotyledons usually store reserve-food in their cotyledons, which may in germination remain below ground (hypogeal).
The process of liming, which originated at the time when the Dutch held a monopoly of the trade, was with the view of preventing the germination of the seeds, which were formerly immersed for three months in milk of lime for this purpose, and a preference is still manifested in some countries for nutmegs so prepared.
The last measure prevents the germination of the spores of the fungus on the leaves, and is a most useful mode of checking the spread of the disease; to be successful in its use, however, entails care in the preparation of the spray and thoroughness in its application.
- The various phases of germination of spores of Bacillus ramosus (Fraenkel), as actually observed in hanging drops under very high powers.
Germination of spore of Clostridium butyricum - the axis of growth coincides with the long axis of the spore.
G ', g 2, g3, early stages in the germination of the spores (after being dried several days); h2, i, k, 1 and m, successive stages in the germination of the spore.
It is only or germination of the latter that the development of the embryc into the free plant is begun.
If we go back to the first instance cited, the embryo in the seed and its development during germination, we can ascertain what is necessary for its life by inquiring what are the materials which are deposited in the seed, and which become exhausted by consumption as growth and development proceed.
For instance, a Fungus epidemic is impossible unless the climatic conditions are such as to favor the dispersal and germination of the spores; and when plants are killed off owi~ig to the supersaturation of the soil with water, it is by no means obvious whether the excess of water and dissolved materials, or the exclusion of oxygen from the root-hairs, or the lowering of the temperature, or the accumulation of foul products of decomposition should be put into the foreground.
The seeds of West Indian plants are thrown on the western shores of the British Isles, and as they are capable of germination, the species are only prevented from establishing themselves by an uncongenial climate.
Sicily was a favourite haunt of the two 1 Some, however, regard Proserpina as a native Latin form, not borrowed from the Greek, and connected with proserpere, meaning the goddess who aided the germination of the seed.
During April (when the seed is usually sown) and May frequent light showers, which keep the ground sufficiently moist to assist germination and the growth of the young plants, are desired.
In germination the cotyledons come above ground and form the first green leaves of the plant.
The statoblasts require a period of rest before germination, and Braem has shown that their property of floating at the surface may be beneficial to them by exposing them to the action of frost, which in some cases improves the germinating power.
For the germination of the spermatia in nature there is only the observation of Hedlund, that in Catillaria denigrata and C. prasena a thallus may be derived from the spermatia under natural conditions.
The observations of Moller, &c., on the germination cannot be assumed to negative the sexual hypothesis for the sexual cells of Ulothrix and Ectocarpus, for example From Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer.
Forms with septate thallus, and reproduction by chlamydospores which on germination produce sporidia; sexuality doubtful.
The development of the "conidia" as true conidial spores or as zoosporangia may occur in one and the same species (Cystopus candidus, Phytophthora infestans) as in Pythium described above; in other cases the direct conidial germination is characteristic of genera - e.g.
The teleutospore puts forth on germination a fourcelled structure, the promycelium or basidium, and this bears later four sporidia or basidiospores, one on each cell.
(1904); "Zygospore germination in the Mucorineae," Annales mycologici (1906).
The empty fruits (after germination of the seed) are found floating in the Indian Ocean, and were known long before the palm was discovered, giving rise to various stories as to their origin.
Germination of the microspore begins before it leaves the pollen-sac. In very few cases has anything representing prothallial development been observed; generally a small cell (the antheridial or generative cell) is cut off, leaving a larger tube-cell.
The germination of the macrospore consists in the repeated division of its nucleus to form two groups of four, one group at each end of the embryo-sac. One nucleus from each group, the polar nucleus, passes to the centre of the sac, where the two fuse to form the so-called definitive nucleus.
As the embryo develops it may absorb all the food material available, and store, either in its cotyledons or in its hypocotyl, what is not immediately required for growth, as reserve-food for use in germination, and by so doing it increases in size until it may fill entirely the embryo-sac; or its absorptive power at this stage may be limited to what is necessary for growth and it remains of relatively small size, occupying but a small area of the embryo-sac, which is otherwise filled with endosperm in which the reserve-food is stored.
The germination of a zygospore or oospore is effected by the rupture of an outer cuticularized exosporium; then the cell may protrude an inner wall, the endosporium, and grow out into the new plant (Vaucheria), or the contents may break up into a first brood of zoospores.
Their fortuitous dissemination does not always bring seeds upon a suitable nidus for germination, the primary essential of which is a sufficiency of moisture, and the duration of vitality of the embryo is a point of interest.
Among Chlorophyceae it is often the case that the oospore on germination divides up directly to form a brood of zoospores.
The soredia are the most successful method of reproduction in lichens, for not only are some forms nearly always without spore-formation and in others the spores laregly abortive, but in all cases the spore represents only the fungal component of the thallus, and its success in the development of a new lichen-thallus depends on the chance meeting, at the time of germination, with the appropriate algal component.
In germination of the seed the root of the embryo (radicle) grows out to get a holdfast for the plant; this is generally followed by the growth of the short stem immediately above the root, the so-called "hypocotyl," which carries up the cotyledons above the ground, where they spread to the light and become the first green leaves of the plant.
Soil whose temperature remains low, whether from its northerly aspect or from its high water content or other cause, is unsatisfactory, because the germination of seeds and the general life processes of plants cannot go on satisfactorily except at certain temperatures well above freezing-point.