Host plant

“ On the south side of his shop, two large doors open into a roomy, glass-roofed hot house, containing a very unique collection of potted plants, which, under the skillful hands of this young enthusiast, are undergoing the different stages of experimental treatment, such as he may deem necessary, to prove or disprove his many pet theories or fancies, in regard to care, growth, insect enemies, and to application of electric light, sun light, heat, moisture and fertilizers. Each plant bears a fruitful crop of cards, giving a summary of results and conclusions. ”

“ A small portion of air to be admitted on fine days, to purify the atmosphere of the house. Keep the surface of the soil in the pots free from weeds, as also from moss and lichen; but when doing so do not loosen the soil so as to injure the roots near the surface. Keep every plant free from dead leaves, and all climbing plants neatly tied up. The Achimenes, Clerodendrons, Erythrinas, Gloxinias, and the various bulbs will now be approaching a state of repose, and therefore will require but little or no water. ”

“ Second, seeds are transported by water across oceans, &c. when they can be floated on any material by which they are preserved, as by wrecks and masses of wood, which have been washed down the rivers.
Third, they are conveyed by man to all parts of the globe.
Fourth, a period of latency is observed to apply to them, that is, they require certain essential conditions before germination occurs; so that even in some localities, a plant may not have been known to exist in a particular neighbourhood, but by a train of circumstances, it may make its appearance, and again be a centre of development. ”

“ In the first place, the enormous holdfast, ensured by the millions of points of adherence, enables the plant to withstand even powerful lever actions from above, and provides fixed points against which the root-tips can work as they drive deeper into the soil. In the second place, the intimate contact of the root-hairs and particles of soil, ensures that the films of water held by surface-action on the soil-particles and root-hairs shall be in continuity with the water saturating the cell-walls of the latter, and therefore with the protoplasm and cell-sap in their interior. ”

“ As only a comparatively small number of plants can reproduce by this method, it is obvious that something more must be provided to secure new generations of plants. Flowers, and the fruits and seeds which inevitably follow them, do this. All plants, with some exceptions to be noted later, produce flowers at some time in their life. In the case of the century plant, only once, after which they die. But except for ferns, mushrooms, seaweed, yeast, bacteria, and some other forms of so-called flowerless plants, a flower or blossom is to be found at some stage in the life of all plants. ”

“ As a rule, it is not desirable to have either seeds or seedling plants in the ground for any length of time when the temperature is too low for active vegetation; for while they rest, other, lower organisms (fungi and bacteria) , adapted to low temperatures, may continue in full activity at the expense of the vitality of the crop plant. ”

“ Only the head and six prolegs of the occupant ever emerge from its case. Dragging its house along upon the plant, it attaches the open mouth of the sack close to the green seed-pod, after which the shell is gnawed through at the point of contact, and the young seeds devoured at pleasure, when a new journey is made to the next capsule, and thus until the maturity of the larva. ”

“ Every pool, every soil, swarms with bacteria, the lowliest form of life—organisms exceedingly minute, exceedingly simple, and capable of existing under highly diverse conditions both physical and chemical. Thence we can trace an irregular ascending scale through the Fungi, the Algæ, Mosses, Horsetails, Ferns, and Club-mosses, to the Conifers, and on to the highest of the Seed Plants, which exceed in their beauty of structure and complicated life anything that has gone before them. ”

“ The difficulty is very often to know where to draw the line. Probably no flowering plant is quite independent of the labour and work of its neighbours. As we have tried to show in another chapter, a long preliminary cultivation by bacteria, lichens, and mosses is required before flowering plants can develop on bare rock. That is also necessary in all cases where the soil is mineral or inorganic, without any organic dust or fragments of vegetable or animal matter. Bacteria must always begin the work by preparing nitrates and other salts. ”

“ It is quite certain, that if a healthy seed, or leaf-bud, be placed in such a situation, that, according to the laws known, it will in all likelihood germinate, if all the elements for its sustenance exist in the soil, and the temperature and hygrometric {144}condition of the atmosphere are adapted to it, a healthy plant will be the result. ”

“ A large family having characteristic pealike flowers, a description of which has already been given in Chapter I. They all bear legumes, a pod that splits down one side, not both, as in Brassicaceæ. Besides the pea, the bean, vetch, alfalfa, lentil, locust tree, and dozens of valuable timber trees in the tropics belong here. Flowers all showy and absolutely dependent upon insects for fertilization. Seeds highly nutritious in many genera, and the roots of nearly all have bacteria associated with them. (See chapter on Food Habits of Plants.) ”

“ Numerous plants and trees are propagated to an unlimited extent by cuttings and buds; and we have sundry plants which cannot be otherwise propagated. The most familiar are the double roses of our gardens: these do not seed, and yet have been distributed everywhere by grafts and buds. Hothouses furnish many cases, as I learn from an authority second to none. Of "the whole host of tropical orchids, for instance, not one per cent. has ever seeded, and some have been a century under cultivation." ”

“ And in the woods at this season you find the yellow adder’s tongue, spring beauty, anemone, wake-robin, Jack-in-the-pulpit, wild ginger, and Solomon’s seal. Each of these plants has stores of food hidden in its [Pg 217] underground stem. This may take the shape of a bulb, or a tuber, or a rootstock; but in any case it shows you at once that it is a little storehouse of food.
A collection of the different kinds of underground stems which serve as storehouses for the early-flowering plants would be quite as interesting to work over as a collection of plant packages. ”

“ The moment, however, that the roots of one enter the area from which the other draws its water supply, or the foliage of one begins to overshade the leaves of the other, the reaction of the former modifies unfavorably the factors controlling the latter, and competition is at once initiated. The same relation exists throughout the process; the stronger, taller, the more branched, or the better rooted plant reacts upon the habitat, and the latter immediately exerts an unfavorable effect upon the weaker, shorter, less branched, or more poorly rooted plant. ”

“ Actually what are ordinarily thought of as plants make up only a fraction of the great plant world. The fact that our familiar roadside and garden plants produce blossoms followed by a fruit and seed, such as peas and beans and all the ordinary flora of any region, separates them at once from that other large group of plants that do not. Common examples of the latter class are the green scum on the ponds, moss, seaweed, the rust on wheat, yeast, disease-causing bacteria, the smallest of all known plants, and many others. ”

“ It is clear that while many species accommodate themselves easily to different soils or different degrees of light or of moisture, others have small powers of accommodation, and are in consequence restricted in their range. By long usage many plants have acquired special characters enabling them to live under special conditions—some examples will be discussed a little later—and in some such cases it is easy to correlate the peculiar characters of the plant with those of the habitat. ”

“ Light, heat, moisture, and soil are therefore to be considered as the agents required to exist in a certain balance, or proportion, in reference to the health or power of vitality of the plant. Within a certain amount of variation, health may persist in virtue of the power of selection, which appertains to the spongioles of the root in absorbing nutriment; and also as regards light, from the tendency which most plants have to accommodate themselves to any deficiency of this element, by presenting their leafy expansion in that direction where the most of its influence may be obtained. ”

“ Plants must live together. They associate; they become adapted or accustomed to each other. Some can live in shade; they thrive in the forest, where sun-loving plants perish. Others prefer the sun, and thereby live together. There are plant societies.
Fig. 252. Weak, narrow-leaved grasses grow in the cat-tail forest.
Every distinct or separate area has its own plant society. There is one association for the hard-tramped dooryard,—knot-weed and broad-leaved plantain with interspersed grass and dandelions; one for the fence-row,—briars and choke-cherries and hiding weeds ”

“ You know that they are stowing away their food in warmer, safer places than can be supplied by the delicate leaves. And when all the food has been drawn out of the leaves, and packed away in the right spots, then the plant finishes a piece of work it began some time before. This piece of work is the building-up of a row of little cells just where the leafstalk joins the stem or branch. When this row is complete, it acts almost like a knife, loosening the stalk from the stem. ”

“ Reproduction and the ultimate scattering of fruits and seeds are absolutely necessary in order that colonies of plants may reach new localities. It is evident that plants best fitted to scatter their seeds, or place fruits containing the seeds some little distance from the parent plants, are the ones which will spread most rapidly. A plant, if it is to advance into new territory, must get its seeds there first. Plants which are best fitted to do this are the most widely distributed on the earth. ”

“ God gives the seed a body "as it hath pleased Him, and to every seed its own body."
It is true that what are called "varieties" can be produced among cultivated plants, as among birds and animals, by change of food and climate, and by care and training. The same plant will soon look very different if taken from a dry, sunny spot, and placed in a damp, shady corner. I have heard that if plants are moved from their home on the seashore, and placed in a dry, hot place, their thick, fleshy leaves will in time quite change their character, becoming thin and hairy. ”

“ The Simplest Plants.—We have seen that perhaps the simplest plant would be exemplified by one of the tiny bacteria we have just read about. A typical one-celled plant, however, would contain green coloring matter or chlorophyll, and would have the power to manufacture its own food under conditions giving it a moderate temperature, a supply of water, oxygen, carbon dioxide, and sunlight. ”

“ The groups of the Mosses, Hepatics, and Ferns, which are more highly organized than the Fungi, possess chlorophyll, and manufacture their own food; and it is with some little surprise, therefore, that when we come to the Seed Plants, the highest group of all, we find, though in relatively few cases, a reversion to the animal trait of using organic food. ”

“ The seed-beds must be tended with scrupulous care to keep down weeds and avert other dangers. It is of great importance to secure a robust plant, short, full of colour, and free from club at the root. ”

“ It is now necessary to look at the subject from the viewpoint of the horticulturist—​that is, the relationships of the animals to their surroundings, or environment, and to the welfare of man. Of the two great life-groups—​animals and plants—​the plants are of fundamental importance; without them no animal could exist, since, of all living things, it is the green plants alone that are able to convert the inorganic chemical constituents in soil, air and water into living matter or protoplasm; and all animals, either directly or indirectly, are dependent upon plants for their food supply. ”

“ Of course the factors of favorable or unfavorable conditions, once the seed is deposited in the new home, operate to keep plants from the tropics from settling permanently in colder regions and vice versa, but we cannot escape the conclusion that the sky is filled during certain seasons with millions of seed carriers that have, in many cases, populated their stopping places with foreign plants.
Other animals than birds carry fruits and seeds, besides those that eat them. ”

“ Each of these cells can act as a separate plant, drinking in the water and air it needs, and feeding and growing quite independently of the roots below. Yet at the same time the moss stem has a great advantage over single-celled plants in having root-hairs, [Pg 88] and being able to grow upright and expose its leaves to the sun and air. ”

“ Plants must be collected both in flower and in fruit, with the underground parts as perfect as may be. Seedlings and rosettes should be included whenever present. In pressing, one or two leaves should be arranged with the lower side uppermost to admit of the ready comparison of both surfaces. Opened flowers are valuable for flower biology, while seeds and fruits are desirable for showing migration contrivances. The ferns, mosses, and lichens of the formation should be fully represented, together with the more important fungi and algae. ”