A classification or orderly arrangement of material collected for study is indispensable to true pleasure and profit. The nature student must classify both his specimens and the knowledge he may obtain about them ; for, as Spencer has said, "When a man's knowledge is not in order, the more of it he has the greater will be his confusion of thought." As he compares his specimens he sees interesting gradations of resemblance, and becomes fascinated with the pleasure of tracing their relationships and the gradual evolution of higher forms from lower.
Every lover of nature who haunts the fields and woods acquires a rich store of facts about plant life, and without, perhaps, recognising that he does so, distinguishes two great groups of plants- those which have attractive flowers, and those which have no flowers at all. His flowerless plants bear no seeds, but quantities of fine, dust-like particles which rise in the air as he brushes his stick over their green leaves. As the powers of observation develop, he distinguishes the ferns and Christmas greens among flowerless plants, and perhaps soon recognises that the soft green moss bank, too, is composed of small plants, and that the green mats, the liverworts, on stones and moist banks and logs, are plants also. His only reason, perhaps, for calling them plants is that they grow and are green. He may learn with the microscope that the pond scums which he had thought disgusting frog-spittle are in truth tangles of exquisite plants, made up of chains of slender, transparent cells finer than silken threads, each cell containing many tiny green particles of leaf green, or chlorophyll - the cause of the green colour of all green plants.
Corollas and honey, attractive to insects.
At first the most conspicuous plants attract the attention, and afterwards, in succession, those less and less conspicuous. They, in reality, present themselves in great natural groups, readily distinguished by well-marked characteristics.
It will be seen, as these pass in review, that they are conspicuous according as they are complex. The gorgeous flowering plants have complicated methods of reproduction - corollas and honey, attractive to insects ; ingenious stamens, pistils, seed-boxes, and seeds. The humble grasses, with their close relatives, dispense with gay colours and the assistance of insects, and trust to the breezes to carry their pollen to its goal. The pines and their allies are a step nearer simplicity, and do not enclose their seeds in a seed-box at all, but provide them with wings for dissemination, and leave them exposed to the wind.
Pistil of violet.
Pistil of St. Johns-wort.
Seed-box of sacred bean.
Winged seed of the silver fir.
Seed-box of iris.
Fern with spores (Polypo-aum vulgare).
The ferns and Christmas greens (Lycopodiums) have no flowers, and therefore no true seeds. They have a distinct stem, which grows from the apex and is strengthened by woody fibres, which may readily be seen by breaking the stem across. The woody fibres so strengthen the tissues of these plants that they are able to stand erect and make a conspicuous appearance not possible to the small mosses and liver w o rts , which are spore-bearing plants with no woody fibre.
The plants of all these groups resemble each other in descending degrees, so that they may be classed in groups under groups. Similar specimens may form groups of species. Species may form larger groups, or genera. Genera with common characteristics may form families ; and groups of families, orders; and orders, classes ; while classes unite to form branches, or phylae.
A botanist relies for the classification of his specimens mainly upon the similarity of those parts of the plant which produce the seeds or spores rather than upon those parts - the roots and leaves and stems - which have the work of the plant household to do. He finds that the seed and spore producing parts are more constant in their forms and habits than the leaves and stems and roots, which are more exposed, and which are constantly being forced to a change of form which will better suit their changed surroundings.
Bean seed open to show embryo.
Liverwort (Marckantia polymorphd)
Moss (Dicranum scopariuni) (natural size).
The novice sees nothing in the brown, or even in the highly coloured, fungi to warrant his calling them plants. They are to him "just toadstools ;" for green colouring matter - his first criterion for plants- is not there, and, moreover, there is nothing in their shape which suggests to him the plants with which he is familiar. The snow-white Indian pipe lacks the green of most plants, but that does not rule it for him out of the plant world ; for although it is colourless, and depends upon other plants for food, still it has a flower form and produces a seed-box with well-developed seeds. Fungi, however, to any but the close student must seem quite unrelated to all normal plant forms. But the botanist, by a study of their structure, finds that they all grow from microscopic, dust-like particles, which differ from true seeds in consisting of but one or a few cells, and in having no embryo plant in them as true seeds have. He recognises their position in the kingdom of living things, and classes them as spore-bearing plants, lower than the group of mosses, those dainty plants which delight every one with their gracefulness, and which bear their spores in tiny capsules or boxes set up on slender stems. By studying their life history he decides that they are degenerate members of the lowest group- the algse-and that they have fostered the habit of feeding on material constructed by green plants, instead of constructing food material for themselves, and have, in consequence, lost their power of constructing such food, and also their green granules by which this work of construction may be carried on.
White mould on dead fly.
The life history and structure of fungi has been studied so minutely that one is able to arrange them in three well-marked classes:
The first class, the algal-like fungi (Phycomycetes), includes bread moulds and several of those fungi which cause diseases of plants and animals - the downy mildew on the grape, the potato rot, the common white mould which fastens dead flies to the walls or window panes in the autumn, and the fungus which grows on salmon and causes them to die in great numbers. The plant of these fungi is cobwebby, sometimes growing within the cells of the plant substance on which it lives, and sometimes growing both within and on the surface. A freshly moulded piece of moist bread shows the bread covered with exquisitely fine transparent threads, which constitute the plant. Later, spore cases containing tiny black spores will be seen, which give a delicate gray tint to the plant at first, but later form a black, repulsive mass as their numbers increase. These plants are regarded as descendants of degenerate algae, which lost their power of independent existence through stealing their food instead of making it for themselves.
The second class, the spore-sac fungi, produce their spores in delicate membranous sacs. The spore-sac fungi vary greatly in size, habit, and structure. Most of them are inconspicuous members of the plant world, as the yeast plant, by which our bread is raised ; the fungus which causes the peach leaves to curl and the black knots to appear on cherry and plum trees.
The third class is made up of all fungi which bear their spores on little spicules standing up on large cells. This contains most of the conspicuous fungi one will care about knowing. To understand the group one must understand the method by which a spore grows to be a fungus plant, and to be able to distinguish the different members of the group one must know on just what portions of the spore receptacle the spores are borne.
Spore cases, Threads, Bread mould (magnified).
Spores borne in delicate membranous sacs (magnified).
Spores borne on little spicules (magnified).