This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
Inflorescence is the ramification of that part of the plant intended for reproduction by seed, and the reproductive organs of plants are the flowers. Extremely varied indeed are the forms of inflorescence, in some cases simple, but in most cases compound. In the Tulip it is simple, and the peduncle supports but one solitary terminal flower. A raceme has an inflorescence in which the flowers are arranged singly on distinct pedicels along a common axis, - ex., Wallflower, many of the Leguminosaa, such as common garden Pea and Glycine (Wisteria) sinensis, Veronica (garden varieties). A spike differs chiefly from a raceme in having its individual flowers sessile - that is, they are not supported by a stalk as in racemes, but lie close upon the body that supports it, - ex., the common Plantain. A compound spike consists of a collection of spikes arranged in a racemose manner. A spikelet is a term used exclusively in describing Grasses, signifying the small terminal collection of florets. A corymb is a form of raceme, in which the pedicels are gradually shorter as they approach the summit, resulting in a flat-headed inflorescence, - ex., Candytuft. An umbel is an inflorescence in which the flowers expand first at the base and last at the end or centre (centripelally), with stalks radiating from a common point, - ex., British Umbelliferse, such as Hemlock, Parsley, Carrot. A cyme is a kind of inflorescence produced by the rays of an umbel forming one terminal flower, and then producing secondary pedicels from below it, the flowers opening first at the end and last at the base, - ex., Chickweeds, Stichworts, common garden Laurustinus. A panicle is an irregularly branched raceme, - ex., Bramble, Horse-chestnut.
Usually, though not invariably, the corolla forms the most ornamental part of plants, the parts of which are termed petals, which are extremely varied and numerous in form. In some the corolla or petals are polypetalous - that is, each part is separate from the other : those of the Ranunculus are polypetalous, and are regular in form, shape, and size. All representative British orders of the division Thalamiflorae have their petals polypetalous, including such orders as Ranunculaceae, Cruciferse, Violaceae, and Caryophyllaceae, the greater portion of which contain regular flowers. Those of Violaceae, and a few others, including Fumariaceae, have their flowers irregular. In the common Primrose the flowers are gamopetalous, and still regular. In some cases the flowers may be labiate, as in the Mints (Menthas), Deadnettles, (Lamiums), etc.; calceolate, as in Cypripedium calceolus; campanulate, as in the Harebells (Campanulas); ringent, as in the Linaria vulgaris; papilionaceous, as in leguminous plants - Pea, Bean, etc.; funnel-shaped, as in the Polyanthus and many others. Some plants do not possess any petals or sepals whatever, but are included in the division Achlamydeae, which contains several of our native trees, such as the Birch, Willow, Scotch Fir (Abies excelsa), etc.
In some cases the female (pistil) and male (stamen) flowers are borne on a separate plant, which is termed dioecious : when borne on the same tree, but in different flowers, it is called monoecious. In the Arum maculatum, a common British plant, the stamens and pistils are protected by a spathe.
The blossom is doubtless a beautiful part of the furniture of the plant. Sometimes iridescent with the tints of the rainbow, it revels in the sunbeam, the pride and ornament of vegetation. In respect to size, the flower varies from a microscopic point to a circumference of 9 feet - Rafflesia Arnoldii being quite that. In the shape of many-Orchises can be seen the forms of various insects and animals, such as the lizard, frog, wasp, spider, man, grinning monkey, fly, bee, etc., presenting the forms mentioned to perfection. W. Roberts.
(To be continued).