Proteaceae

“ In my general observations on Proteaceæ I have noticed two very remarkable characters of Synaphea, namely, the cohesion of the barren filament with the stigma, which is peculiar to this genus, and the structure and connection of the antheræ, in which it agrees with Conospermum: it is also remarkable that these two nearly related genera should differ in the position of their barren and fertile stamina with relation to the perianthium; plants of the same natural family very generally agreeing in the order of abortion or suppression of these organs ”

“ The natural order of Proteæ, or, as it is less exceptionally called, Proteaceæ, was first established in the Genera Plantarum of the celebrated Jussieu; and the description there prefixed to it will, with a few alterations, still apply to the order, now that it has received so many additions, not only in species, but in very distinct genera, several of which were first published by
Dr. ”

“ This polarization provides strong evidence that actinomycetes and neomura together form a clade, which I designate 'proteates' because the proteasome with core 7-fold symmetry is its synapomorphy, and thus excludes the root of the tree of life from anywhere within proteates. One can hardly suppose that the complex proteasome core was the ancestral state for all life and that monomeric NTN hydrolases ultimately evolved from it via HslV and two progressive simplifications involving a change of chaperone partner and then its loss. ”

“ He proved that the prothallus is one of two generations in the life-history; that it begins with a spore and ends with a fertilised egg-cell; that in the higher cryptogams there is a regular alternation of generations; that the prothallus of the fern answers to the leafy moss, while the leafy fern is the equivalent of the moss-capsule; that the egg-cell is the same structure in both cryptogams and flowering plants; that the pollen-tube and the seed are found to-day only in flowering plants ”

“ 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. ”

“ Among gymnosperms it is not difficult to see that it consists of the pollen-grain and the embryo sac with its endosperm. The male prothallus is reduced and rudimentary, and one cell of the pollen-grain, representing the antheridium, produces a tube instead of antherozoids. The endosperm is the female prothallus, and in it the germ-cell develops. The asexual generation is the plant that grows from the fertilized germ. In the angiosperms the sexual generation is reduced to its simplest form, namely, a single cell for the male part, and one or a few cells for the female. ”

“ To botany and zoology is now added protistology.
The name “protists” (from protiston, the very first) is familiar to every one in biology to-day. If protistology has not yet been securely established as a special branch of science, that is due to the circumstance that a strict limit cannot be determined on either the plant or the animal side, so that the botanist encroaches on the province at one point and the zoologist at another. ”

“ The second key criterion that is used to polarize the evolutionary transition and place the root of the tree within negibacteria is the distribution of the proteasome core particle. It is present in archaea (20S proteasome) , in eukaryotes (26S proteasome) and in some, but not all, actinobacteria (high GC Gram positive) . The two, α and β subunits, are distantly related to HslV, a protein widely distributed in bacteria, although absent from cyanobacteria and chlorobacteria (chloroflexi) . ”

“ The ultimate step, as we must suppose, is the formation of living protoplasm out of these non-living proteids. A cardinal fact is that proteids admit of multitudinous transformations; and it seems not improbable that in protoplasm various isomeric proteids are mingled. If so, we must conclude that protoplasm admits of almost infinite variations in nature. Of course pari passu with this dual process—augmentation of protoplasm and accompanying production of carbo-hydrates—there goes extension of plant-structure and plant-life. ”

“ 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. ”

“ It is not always easy to tell whether certain organisms are plants or animals, and because of this some scientists have suggested that these “in-betweens” be placed in a separate kingdom—the Protista. The protistans are primarily unicellular organisms and are represented by such forms as bacteria, algae, diatoms, and the protozoans (see below) . ”

“ 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. ”

“ The protoplasm of the living plant-cell looks like a slimy translucent mass which has been superficially compared in appearance to well-boiled sago or clear gum. Fifty years of observations and experiments with it have convinced physiologists that it is not a mere solution or emulsion, however, or even a chemical compound in the ordinary sense of the term, although chemical analysis gets little out of it beyond water, proteids, carbohydrates and fats, and traces of certain mineral salts ”

“ From the first discovery of the Protozoa, their life-history has been the subject of the highest interest: yet it is only within our own times that we can say that the questions of their origin and development have been thoroughly worked out. If animal or vegetable matter of any kind be macerated in water, filtered, or even distilled, various forms of Protista make their appearance; and frequently, as putrefaction advances, form after form makes its appearance, becomes abundant, and then disappears to be replaced by other species. ”

“ The spores grow slowly when they come on to moist earth, but as their development takes a long time, you had better get some from a gardener which have already grown. As the spore grows, the one cell composing it divides and divides again, until there is formed a little filmy heart-shaped green structure called a prothallium (see fig. 129) , which is not in the least like a fern plant, for it is not more than a quarter of an inch across. It has no stem or leaves, and is only a thin layer of green cells, with a few root-hairs on the under side. ”

“ In this Natural Order, we find fruits and seeds, of very different sizes as well as shapes, but fortunately they are so similar in species of the same genus, that a gardener who is not learned in botany, after having seen one of each, may have a tolerable guess, at the genus of any new ones, he receives from abroad. In sowing them, much must be left to the discretion of the gardener; generally they ought not to be buried deeper than half an inch in the earth, nor closer to each other, than from a quarter of an inch to an inch, according to their size ”

“ The first generation proceeds directly from the spore, and consists of a simple green expansion which is short-lived and very small, not usually exceeding half the size of a small finger-nail. This prothallus, as it is termed, has small, root-like hairs which fix it to the earth or elsewhere. The prothallia are to be seen in large numbers on the sides of flower-pots in neglected greenhouses. Each little green scale is a young fern-plant during its sexual generation. The male and female organs are much the same shape as those of mosses. ”

“ Even admitting that there are protoplasts (using this word to include plant and animal types) which are without nuclei, still they are not homogeneous—they are granular. Whether a nucleus is always present is a question still undecided; but in any case the types from which it is absent are extremely exceptional. Thus the most general structural traits of protoplasts are—the possession of an internal part, morphologically central though often not centrally situated, a general mass of protoplasm surrounding it, and an inclosing differentiated portion in contact with the environment. ”

“ Both in the plant-world and in the animal-world there are types in which we see little more than simple assemblages of Protophyta or of Protozoa—types in which the units, though coherent, are not differentiated but constitute a uniform mass. In treating of structure we are not here concerned with these unstructured types, but may pass on to those aggregates of protoplasts which show us differentiated parts—Metaphyta and Metazoa: economizing space by limiting our attention chiefly to the last. ”

“ Classification.—The classification of the Protozoa is no easy task. We omit here, for obvious reasons, the unmistakable Plant Protists that have a holophytic or saprophytic nutrition; that are, with the exception of a short period of locomotion in the young reproductive cells, permanently surrounded with a wall of cellulose or fungus-cellulose, and that multiply and grow freely in this encysted state: to these consequently we relegate the Chytridieae, which so closely allied to the Proteomyxa and the Phycomycetous Fungi ”

“ Seed-bud and pointal.
Throughout this small divided-leaved section of the genus Protea there is a similarity of appearance in the foliage, that makes the specific differences appear less distinct than they really are. The small-flowered species is a compact bushy little shrub, about fourteen inches high, and nearly the same in width, requiring a light sandy loam, free access of air, and a little attention to preserve it from the partial humidity of the atmosphere. ”

“ The sperm-cells escape from the antheridium and in the water that collects on the prothallus are carried to the archegonium, where fertilization of the egg takes place. From the fertilized egg-cell a plant grows, becoming a “fern.” In most cases the prothallus soon dies. The prothallus is the gametophyte (from Greek, signifying the fertilized plant) .
The fern plant, arising from the fertilized egg in the archegonium, becomes a perennial plant, each year producing spores from its fronds (called the sporophyte) ”

“ The spore on germination gives rise to a small thalloid structure, the prothallium, on which the sexual organs are developed; this is the gametophyte or sexual generation. The sexual organs have the form of typical archegonia and antheridia. From the fertilised egg-cell there is developed the Pteridophyte plant or sporophyte, which bears the spores. This asexual generation shows a well-marked external differentiation into stem and leaves, and bears true roots. Internally the tissues exhibit a high degree of differentiation into distinct tissue-systems. ”

“ This attracts sufficient moisture to burst open the outer, and then it begins to increase by the subdivision of its cells, until the primary green prothallus D is formed. This falls to the ground, and, being furnished on its under side with thread-like fibres, fixes itself to the earth, and thus is developed the rhizome, or root of the future plant. In each of the antheridia, which are numerous, a cell is formed, chiefly filled with albuminous matter and free spores, each having attached a flat ribbon-like filament, or stermatoid, curled in a spiral manner. ”

“ The prothallus is exceedingly small, being little more than a group of cells forming an antheridium. Should there be sufficient moisture about, the spermatozoids which are produced by the antheridium swim towards the archegonia in any female prothallus which may be near. Fertilization then takes place, and the final outcome is the young plant. Now and again in certain species it is seen that the megaspores develop to such an extent within the sporangium that fertilization [21] takes place, and even an embryo or young plant may be formed. ”

“ All the great mass of Protista, the Monera, Amœbæ, Myxomycetes, Rhizopoda, etc., in short, all the lower organisms which we shall have to enumerate in the domain of Protista, standing midway between the animal and vegetable kingdoms, propagate themselves exclusively in a non-sexual manner. And this domain comprises a class of organisms which is one of the richest in forms, nay, even in a certain respect the richest of all in forms, as all possible geometrical fundamental forms are represented in it. ”

“ The spores germinate on moistened ground. In a conservatory they may be found germinating on a damp wall or on the edges of a well-watered flower-pot. Instead of directly forming a fern-plantlet, the spore grows first into a body which [Pg 160] closely resembles a small Liverwort. This is named a Prothallus (Fig. 509) : from some point of this a bud appears to originate, which produces the first fern-leaf, soon followed by a second and third, and so the stem and leaves of the plant are set up. ”