364. Definition. In the bud the floral leaves (sepals and petals) infold the floral organs (stamens and pistils) and conceal them from view. Flowering consists of the opening or expansion of these envelops, displaying every organ now perfected in growth and beauty, and ready for the exercise of its function.
365. Period of flowering. Each species of plant has its own special season for flowering, uniform in the same climate, but varying in different climates according to the general temperature. Hence each month and each day of the month mark the date of flowering for some one or more species, and these facts, when duly observed and recorded in their proper order, constitute the floral calender for that locality.
366. The floral calendar is an index of climate, and may vary to a considerable degree in different years for the same locality or for different localities in the same year. Such a calendar is prepared by the botanical student when he carefully journalizes his discoveries from day to day throughout the season.
367. Examples. At Savannah the red maple, shad-bush, blood-root, flower in February; in the District of Columbia in March; at Concord, N. H., in April. In New England the witch-hazel flowers in February; Hepatica in April; dogwood in May; elder in June; lilies in July; boneset in August; asters and Solidagos in September and October; and chrysanthemum in November.
368. The floral clock. Each plant has also its definite hours in the day for opening its flowers and for closing them - for waking and sleeping; and a careful record of these facts (as once made by Linnaeus) may seem to indicate the hour of the day. Thus,
The morning glory opens at
2 A. M.,
10 A. M.
Rutland beauty "
Vegetable oyster "
Scarlet pimpernel "
Calendula arvensis "
Arenaria rubra "
Ornithogalum umbellatum "
2 P. M.
Marvel of Peru "
Silene noctiflora "
Evening primrose "
Lychnis vespertina "
Cereus grandiflora "
369. The colors of flowers constitute one of their chief attractions, and are of special interest to the florist. By various modes of culture he may often change at will those colors, thus producing numerous varieties, as in the tulip and dahlia. But in scientific descriptions the colors are seldom employed as characteristics on account of their variableness.
370. Classification of colors. De Candolle divides the colors of flowers into two series; 1, those having yellow for their type and capable of varying to red and white, but never to blue; 2, those having blue for their type, and capable of varying to red and white, but not to yellow. The first series is called Xanthic, the second, the Cyanic. Both series commence with green (which is composed of blue and yellow) and end in red, thus:
371. Examples. The tulip wa3 originally yellow. All its numerous varieties are of the xanthic series. So also the rose and Dahlia. Florists have never yet obtained a blue tulip, rose, or dahlia. The geranium varies throughout the cyanic series, and a yellow geranium is unknown. Different species of the same genus may belong to different series, so also different parts of the same flower.