Pheromone

“ Some, indeed, have gone so far as to postulate something like consciousness which controls and directs the formation of protoplasm, and the exercise of its distinctive properties in the way of growth, reproduction, and embryonic development into the adapted adult. But the fact remains that wherever analysis has been possible the constituent elements of an organic process prove to be physical and chemical. Protoplasm differs from inorganic materials only in its complexity and in the properties which seem to owe their existence to this complexity. ”

“ If we look at the great groups of plants from a broad point of view, it is remarkable that the fungi and the phanerogams occupy attention on quite other grounds than do the algæ, mosses, and ferns. Algæ are especially a physiologist’s group, employed in questions on nutrition, reproduction, and cell division and growth; the Bryophyta and Pteridophyta are, on the other hand, the domain of the morphologist. Fungi and Phanerogams, while equally or even more employed by specialists in morphology and physiology, appeal widely to general interest on the ground of utility. ”

“ The filaments arising from the carpogonia grow into long thin tubes, which fuse with special cells rich in protoplasm contents; and from these points issue isolated tufts of sporogenous filaments, several of which may form the product of one fertilized female cell. In Naccaria, one of the Gelidiaceae, it is observable that the ooblastema filament, as the tube arising from the fertilized carpogonium has been called, fuses completely with a cell contiguous to the carpogonium before giving rise to the foraging filaments already referred to. ”

“ Occasionally in the same plant that bears tetraspores, but more commonly in special ones, there are produced the sexual organs, and subsequently the sporocarps, or fruits, developed from them. The plants that bear them are usually stouter that the non-sexual ones, and the masses of ripe carpospores are large enough to be readily seen with the naked eye.
If a plant bearing ripe spores is selected, the young stages of the female organ (procarp) may generally be found by examining the younger parts of the plant. The procarp arises from a single cell of the filament. ”

“ The long multicellular hairs are not so quickly affected. After a leaf had been left in a weak infusion of raw meat for 10 hours, the cells of the papillae had evidently absorbed animal matter, for instead of limpid fluid they now contained small aggregated masses of protoplasm, which slowly and incessantly changed their forms. A similar result followed from an immersion of only 15 minutes in a solution of one part of carbonate of ammonia to 218 of water, and the adjoining cells of the tentacles, on which the papillae were seated, now likewise contained aggregated masses of protoplasm. ”

“ By careful focusing it is easy to show that the protoplasm is confined to a thin layer lining the wall, the central cavity of the tube being filled with cell sap. In the protoplasm are numerous elongated chloroplasts (cl.) . and a larger or smaller number of small, shining, globular bodies (ol.) . These latter are drops of oil, and, when the filaments are injured, sometimes run together, and form drops of large size. No nucleus can be seen in the living plant, but by treatment with chromic acid and staining, numerous very small nuclei may be demonstrated. ”

“ Pyrenoids occur in some. Starch is never formed in the chromatophores themselves, but a modification—Florideæ starch—may be found in the colourless protoplasm. Asexual reproduction by motile or motionless spores (tetraspores) which are devoid of cilia and of cell-wall. Swarmspores are never found.
Sexual reproduction is wanting, or takes place by the coalescence of a spermatium and a more or less developed female cell. The spermatia are naked masses of protoplasm, devoid of cilia and chromatophores. ”

“ Comparing this now with the development of the sporogonium in the bryophytes, it is evident that the young fern is the equivalent of the sporogonium or spore fruit of the former, being, like it, the direct product of the fertilized egg cell; and the prothallium represents the moss or liverwort, upon which are borne the sexual organs. In the fern, however, the sporogonium becomes entirely independent of the sexual plant, and does not produce spores until it has reached a large size, living many years. ”

“ Thus, the animal can only raise the complex substance of dead protoplasm to the higher power, as one may say, of living protoplasm; while the plant can raise the less complex substances—carbonic acid, water, and nitrogenous salts—to the same stage of living protoplasm, if not to the same level. But the plant also has its limitations. Some of the fungi, for example, appear to need higher compounds to start with; and no known plant can live upon the uncompounded elements of protoplasm. ”

“ They maintain their individuality by a simple metabolism; they grow by the addition of fresh plasm obtained by it, and they split up into two equal globules of plasm when the growth passes a certain limit—reproduction by clevage, maintenance of the species. Thus these chromacea have neither special organs, or organella, that we can distinguish in their simple plasma-bodies, nor different functions in their life-process; it is wholly taken up with the primitive work of their vegetal metabolism. ”

“ If a little of the fermenting liquid is examined microscopically, it will be found to contain great numbers of very small, oval cells, with thin cell walls and colorless contents. A careful examination with a strong lens (magnifying from 500–1000 diameters) shows that the protoplasm, in which are granules of varying size, does not fill the cell completely, but that there are one or more large vacuoles or spaces filled with colorless cell sap. No nucleus is visible in the living cell, but it has been shown that a nucleus is present.
If growth is active, many of the cells will be seen dividing. ”

“ The protoplasm contains oval masses, which are bright green in color; but the forward pointed end of the cell is colorless, and has a little depression. At this end there is a long vibratile protoplasmic filament (c) , by means of which the cell moves. There is also to be seen near this end a red speck (e) which is probably sensitive to light. A nucleus can usually be seen if the cell is first killed with an iodine solution, which often will render the flagellum (c) more evident, this being invisible while the cell is in motion. The cells multiply by division. ”

“ Not only does a moss-plant never arise directly from the spore, but in all cases of vegetative reproduction, apart from the separation of branches by decay of older regions of the plant, a protonema is found. Usually the protonema is filamentous and ceases to be evident after the plants have developed. ”

“ A spore, for instance, can never produce a fern as a seed will always produce a flowering plant. In this respect they are like many insects that always have two or sometimes three different stages in their life history. Only by the complicated method of first a spore then the prothallus, from which archegonia and antheridia are produced, followed by the free swimming male cells fertilizing the female, can a fern reproduce itself. ”

“ While the unstable units of chromatin, ever undergoing changes, diffuse energy around, they may also be units which, under the conditions furnished by fertilization, gravitate towards the organization of the species. Possibly it may be that the complex combination of proteids, common to chromatin and cytoplasm, is that part in which the constitutional characters inhere; while the phosphorized component, falling from its unstable union and decomposing, evolves the energy which, ordinarily the cause of changes, now excites the more active changes following fertilization. ”

“ If the spores are kept in water for a few days they will germinate, bursting the outer brown coat, and the contents protruding through the opening surrounded by the colorless inner spore membrane. The protuberance grows rapidly in length and soon becomes separated from the body of the spore by a wall, and lengthening, more and more, gives rise to a green filament like those we found attached to the base of the full-grown plant, and like those giving rise to buds that develop into leafy plants. ”

“ Fig. 4 is a single elater much magnified, showing it to be a spirally coiled filament, that, by sudden expansion, shoots out the spores just as a child’s toy-gun discharges the arrow. Fig. 5 is a part of the leaf of the Sphagnum moss, common in fresh water, showing the curious spiral arrangement of secondary fibre which is found in the cells, as well as the circular pores which are found in each cell at a certain stage of growth. Just below, and to the left hand, is a single cell greatly magnified, in order to show these peculiarities more strongly. ”

“ This inner mass of cells is continuous with the upper part of the capsule, but connected with the side walls and bottom by means of slender, branching filaments of chlorophyll-bearing cells.
The spores arise from a single layer of cells near the outside of the inner mass of cells (G, sp.) . These cells (H, sp.) are filled with glistening, granular protoplasm; have a large and distinct nucleus, and no chlorophyll. They finally become entirely separated and each one gives rise to four spores which closely resemble those of the liverworts but are smaller. ”

“ He then proved that no injury need accrue to the cell by this process of plasmolysis, since the turgescence can be restored by washing out the salt with a more dilute solution, or with pure water; and the cell may go on living and even growing as before. These phenomena can only be produced in cells where the protoplasmic lining is intact and alive.
Pfeffer showed that the whole matter depends on the properties of the living protoplasmic membrane, which, so long as it is alive, has the power of governing the entrance or exit of dissolved substances, but is as a rule freely permeable for water. ”

“ The conception of chromatin is one based upon its relations to the vital activities and life cycle, as a whole, of the organism or cell, and not upon any definable material, that is chemical and physical, properties.
The importance of protoplasm, as the physical and material basis of life, has caused it to be the subject in recent years of much minute and laborious research. It seems obvious that matter so peculiarly endowed must possess a complexity of structure and organization far exceeding that which at first sight meets the eye. ”

“ The first generation that arose from the spore, the sexual, is in the Muscineae the vegetative plant, while in the Ferns and their allies the whole fulness of vital activity and of morphological differentiation is unfolded in the second generation which is asexually produced. Here all was at once clear and obvious; but Hofmeister's researches also showed that the same scheme of development holds good in the Rhizocarps and Selaginellae where two kinds of spores are formed ”

“ The perithecia are always embedded in a black stroma, and are not distinctly separated from it. The accessory forms of reproduction are: conidiophores, conidiocarps, and yeast-like conidia. The majority are parasites. One order.
Order Dothideaceæ. Phyllachora graminis produces scab-like patches on the leaves of the Grasses.—Scirrhia rimosa grows on the leaf-sheathes of Phragmites.—Rhopographus pteridis on Pteridium aquilinum. ”

“ Such was the condition of affairs with respect to the Algae about the year 1850, when Hofmeister made the formation of the embryo in the Phanerogams, the Vascular Cryptogams, and the Muscineae the central point of investigation in morphology and systematic botany. He made it clear that a perfect insight into the whole cycle of development in the plant and into its affinities can only be obtained, if we succeed in making its sexual propagation, the first commencement of the embryo, the starting-point of the investigation. ”

“ What, then, can be the nature of protoplasm? Struck by its homogeneity, the identity of the elements that compose it with those that form albuminoid substances, it has been taken for a mere chemical compound, and it has been boldly asked if it is not possible to produce it artificially; if man has not power to relight the torch of Prometheus and create life at will. ”

“ The two conjugating elements unite completely, cytoplasm with cytoplasm and nucleus with nucleus, to form the definitive sporoblast or zygote. The protoplasm assumes a definite outline, generally that of an ovoid or barrel, and secretes a delicate membrane, the ectospore. This subsequently becomes thickened, and often produced into rims, spines or processes, giving rise to the characteristic appearance of the Gregarine spore. Internal to the ectocyst, another, thinner membrane, the endocyst, is also laid down. ”

“ The swarm-spores of Algae and Fungi observed by Alexander Braun, Thuret, Nageli, Pringsheim, and De Bary showed that protoplasm is not dependent on the cell-membrane for its vitality, that by virtue of its own internal powers it can alter its form, and even move in space. ”

“ The creepers which are first seen are produced from the germination of the spore. Developing from this, the parasite shews itself on the roots, in the form of a filament or creeper, the outer covering being smooth and dark, while the pith or marrow is white. These creepers take root in the wood, penetrating the pith and spreading out until in the form of a membrane, they fix themselves in the regenerating zone. By some writers this root rot has been given the name of Rhizomorpha subcorticallus. ”