This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Tubular florets gamopetalous, 5-lobed, epigynous, yellow; ligulate florets, gamopetalous, 3-lobed, epigynous, ligule white.
In disk florets only, syngenesious, 5, epipetalous, anther-cells simple.
In ray and disk florets syncarpous, carpels 2, inferior, style 2-fid, arms linear blunt in ray florets, in disk florets short, thick, tipped with papillose cones, ovary 1-celled.
An achene, flattened, inversely ovate, i-seeded.
K(5 - o), C(5), A(5), G(/2).
Floral formulae are designed to show graphically or in abbreviated form the structure of the flower. For this purpose capital initial letters indicate the part of the flower, thus: K = calyx, C = corolla, A = andrcecium, G = gynaecium. Numerals indicate the number of parts, and 00 means indefinite. If there are two whorls in any part the + sign is used. Union of parts is shown by ( ), and adhesion of parts by ( ). Superior parts are shown by a line _ below the figure, and inferior by a line - above (see formula above).
A floral diagram represents the same structure more graphically still. A flower is taken, and the parts are outlined as if seen in transverse section to show their number and relation to each other. The bract is shown in its relative position subtending the flower, as well as bracteoles, and also the axis upon which the flower is borne.
A vertical section of the flower may also be drawn, in which the floral organs are sketched more or less naturally.
Classification of a plant may follow the description. Such work is preliminary to a knowledge of the unit of classification, the species. Flowering plants, according to the Natural System, are called Phanerogams.
This major division includes:
Angiosperms - Ovules enclosed in an ovary. Gymnosperms - Ovules not enclosed in an ovary.
The only native British Gymnosperms are Pine, Yew, Juniper. The Angiosperms include:
Dicotyledons - 2 cotyledons, leaves net-veined, vascular bundles open.
Floral organs in fives, fours, or twos. Monocotyledons - 1 cotyledon, parallel-veined leaves, vascular bundles closed, scattered. Floral organs in threes or multiples thereof.
Dicotyledons and Monocotyledons are subdivided into several sub-classes, and the latter into about ninety natural orders or families (described in Vol. V). It is more difficult to acquire at once a knowledge of these on account of their number, but it should not be difficult even for the tyro to master empirically the characters of many of them without any actual acquaintance with the essential scientific characters of the order. Thus the order Ranunculaceae is not easily confused with many others (save perhaps Cistaceae or Rosaceae) owing to its distinct petals (and sepals) and hypogynous stamens. In Rosaceae the calyx is gamo-sepalous, and the stamens perigynous or epigynous. The order Cruciferae, with 4 petals arranged in cruciform order, is fairly well marked, and has uniformly 4 long and 2 short stamens. The Umbelliferae have a characteristic umbellate inflorescence, 5 sepals, petals, and stamens, and an unmistakable fruit, a schizo-carp, of 2 mericarps.
It is a good plan to master a few orders at a time, and then by a process of elimination the reference of a plant to its natural order becomes less difficult.
More troublesome is the knowledge of genera, the next stage in the classification of plants. Of these the British Flora contains over 500, hence a proper knowledge of these must take time. For a description of these see the summary following that of the natural orders (Vol. V). The relationship of the various divisions and lower grades of classification of plants has already been defined in Vol. I, in the preliminary remarks prefacing the analytical summary.
In studying these different groups one must again emphasize the need for learning their meaning with specimens always, where possible, beside them.
When the species is being studied, in a genus consisting of more than one species (as is usually the case), this becomes most difficult. One must then make use of a good flora (as to which see advice given below).
In studying plants it is almost essential to dissect the specimens to be examined. This at once gives an insight into the structure and the composition of a flower, the part especially important in classification. For this purpose should be procured a knife for cutting sections through a structure. For laying out or separating the parts of a flower, one or two teazers or needles mounted in a match or similar handle are required. A pair of fine-pointed scissors may be used for cutting out fine structures where a knife would be too clumsy. In order, when the various parts are dissected, to keep them flat when laid out on a sheet of paper, glass squares may be used as weights. To fasten the parts down when arranged as in a diagram, one may use gum, water, or other adhesive, or pins.
Small structures may be studied by means of a hand-lens, and a microscope is necessary to examine pollen and small sections, the presence of very small hairs, glands, stomata, crystals, etc.
For lifting very small objects a pin dipped in water or a pair of forceps may be used.
Sketching materials may be employed to draw the flower before dissection, from one or more aspects, as well as after. Painting of the flower to show colour is to be encouraged. Sections, vertical and otherwise, of the flower should be drawn. For these purposes one needs a good Whatman drawing-block, or sketch-book, pencils (H., H.B., &c), and a box of good water-colour paints.
In endeavouring to progress at this stage in the identification of species, two plans may be adopted, one preliminary to the other. One may first proceed from the known to the unknown. Taking a number of field specimens, gathered fresh or herbarium material, of plants known by their English names, study them, write their description, after dissection, etc. Take a flora, in the index look up the English name, and turn to the page where the plant is described. There one will learn its Latin names, discover the natural order and other groupings. Some knowledge is thus gained of the species, genus, natural order, sub-class, class, and one's own description may be compared with that of the flora. If desired, other works can be consulted in the same way, and as much learnt about the plant as possible. It should not after some practice thereafter be difficult to recognize other (unknown) plants of the same genus, order, etc, and to refer them to their proper groups.