This section is from the book "A Dictionary Of Modern Gardening", by George William Johnson, David Landreth. Also available from Amazon: The Winter Harvest Handbook: Year Round Vegetable Production Using Deep Organic Techniques and Unheated Greenhouses.
Two hundred and fifty species. Chiefly green-house evergreens; but a few are herbaceous, and a still smaller number tuberous-rooted. The shrubby evergreens are increased by cuttings: new varieties from seed; and the tuberous-rooted from seed; and all will thrive in a mixture of light loam and leaf-mould. It is to the shrubby evergreens that we shall confine our attention, these being the most beautiful and most generally cultivated. They form a portion of that large family formerly known collectively as "Geraniums;" but modern botanists have divided these into three genera: Pelargoniums, having usually seven stamens, and unequal-sized petals; Geraniums, having ten stamens, and equal-sized petals; and Erodiums, having five stamens.
"The flower should be large, composed of broad rose-leaf petals, free from crumple or unevenness of any kind; smooth on their edges, and forming a compact surface; round which, if a circle be drawn, the perfect symmetry of the flower would appear by the extremity of each petal touching the circle, without extending beyond it. It is indispensable that the flower should be of a stout firm texture, with sufficient liberty at the bottom of the cup to prevent its being in the least cramped; but allowing it to retain, when fully expanded, a fine cupped form, and preventing the falling back or reflexing of the petals. Its colour, whether rich or pale, should possess great clearness: the under petals must be free from veins, and the upper petals should have a large dark spot running to the bottom of them, as destitute as possible of a small white feather, which is usually present, and which greatly impairs the richness of this important part. The beauty of the flower is greatly enhanced by having this spot clearly defined; and if it is surrounded by a dash of crimson, that should have a distinct termination also. The petals ought to be quite free from the least appearance of a watery edge.
Finally, it is essential that the leaves should be large, delicate, and have a healthy appearance; and that the truss should be composed of several flowers, supported by a firm foot-stalk standing quite clear of the foliage." - Gard. Chron.
These are so numerous, fresh varieties appearing annually, that it is useless to attempt to enumerate them; and the attempt is less needed, because each has passed its period of excellence after four or five years. The following are the best that have been introduced during the last two seasons: Alba Perfecta (Thurtell's), white and purple. Arabella (Beck's), white and rose. Aurora (Beck's). Bellona (Beck's), rosy, purple and crimson. Chastity (Beck's).
Desdemona (Beck's), maroon and pink. Desdemona (Thurtell's), claret and white. Defiance (Thurtell's), purplish crimson and white. Dr. Lindley (Foster's). Duchess of Leinster (Gaine's), orange pink, scarlet spot. Emperor Nicholas (Silverlock's). Ezactum (Foster's). Favourite (Beck's), like, but not so good as, Foster's. Gulnare (M'Cormack's), pink and white. Hector (Cock's), rose and white. Isabella (Beck's), pink and maroon. Juno (Beck's), carmine and scarlet. La Polka (Staine's). Lurida (Beck's).
Mark Antony (Beck's), rose and purple. Margaret (Beck's), maroon and pink. 29
Master Peel (Beck's).
Mustee (Beck's), pink, purple spot.
Orion (Foster's), scarlet and maroon.
Othello (Beck's), purple and rose.
Othello (Thurtell's), mulberry and lilac.
Pearl (Catleugh's), white and crimson.
Queen Philippa, rose.
Rainbow (Thurtell's), mulberry and white. Regulator (Thurtell's), violet, purple and white. Rosy Circle (Beck's), dark rose. Satellite (Thurtell's), puce and white. Sir J. Broughton (Foster's). Stromboli (Thurtell's), salmon and purple. Sultana (Foster's), orange and scarlet. Sunset (Beck's), maroon and pink. Superb (Thurtell's), purple and lilac. Titus (Hoyle's), rose and carmine. Trafalgar (Thurtell's), crimson and purple. Unique (Thurtell's), mulberry and white. Zanzummim (Beck's), crimson and flesh. Zenobia (Beck's), rose and mulberry.
 
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