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.
Begonias are most useful for the decoration of sitting-rooms, being highly effective in appearance, and remaining for a long time in good condition. The latter a very important point, as many plants that to all appearances would be suited admirably for rooms when they are taken from the greenhouse, will be found to droop and be anything but ornamental; but this is not the case with Begonias - they will stand a good deal of knocking about. I have some which I keep for this purpose: they have been night after night in hot rooms lighted with gas, and still they seem to keep wonderfully fresh. I grow my plants in a mixture of loam, peat, sand, and well-decomposed manure. They are in pots about 5 inches across, as this size will fit in china-pots or cases of paper, which every one may use for hiding the pot in which the plant is growing. In summer I give them a good supply of water. I give them some all the year round, but not so much as in summer. Some people I know water them overhead, but this I do not think suits them. I have given this practice up, and find the leaves do not so soon turn rusty. Every year I repot them, shaking the old soil well from their roots, and after they have been repotted, place them in a little bottom-heat, so as to start their roots afresh.