Bourbons represent the link between Old and Modern Roses.
[From The Old Rose Advisor, by Brent C. Dickerson, pp. 94: Dickerson provides this entry from Thomas Rivers' The Rose-Amateur's Guide] Monsieur Breon, a French botanist, gives the following account... 'At the Isle of Bourbon, the inhabitants generally enclose their land with hedges made of two rows of roses, one row of the common China Rose [presumably 'Parsons' Pink'], the other of the Red Four-Seasons [presumably the red 'Tous-les-Mois']. Monsieur Perichon, a proprietor at Saint Benoist, in the Isle, in planting one of these hedges, found among his young plants one very different from the others in its shoots and foliage. This induced him to plant it in his garden. It flowered the following year; and, as he anticipated, proved to be quite a new race, and differing much from the above two roses, which, at the time, were the only two sorts known in the island.' Monsieur Breon arrived at Bourbon in 1817, as botanical traveller for the government of France, and curator of the Botanical and Naturalization Garden there. He propagated this rose very largely, and sent plants and seeds of it, in 1822, to Monsieur Jacques, gardener at the Chateau de Neuilly, near Paris, who distributed them among the rose cultivators of France.

[Ibid, p. 94, Dickerson provides this entry written by Monsieur Jacques and published in the Journal des Roses:] "In October or November 1819, I received from the Ile-Bourbon a large collection of seeds of trees and shrubs; they were sent to me by Mons Breon, then chief gardener of the isle's royal possessions, and one of my good friends. In the number were found five rose-hips without any name other than that of 'Rosier del'Ile Bourbon'. At the end of November, I sowed all the seeds in hot-beds, and, along with the others, the roses. Come spring, five individuals came up and, after having been pricked out, raised in pots, and having passed the winter in a cold-frame, two bloomed and rebloomed well enough in the spring of 1821; one had semi-double flowers of a brilliant pink, and served that same year as a model for Redoute's picture, and was then propagated under the name 'Rosier de Bourbon'; the other was also propagated, but wasn't drawn."

[From Old Roses and English Roses, by David Austin, p. 84:] These roses take their name from l'Île de Bourbon, a small island near Mauritius in the Indian Ocean, now known as Réunion. It is said that farmers of this island were in the habit of planting both the 'Autumn Damask' and the 'Old Blush China' together as hedges... there was always a chance that a hybrid would arise, and this, in fact, is what happened. The Parisian botanist Bréon found a rose growing in the garden of a man named A.M. Perchern. This rose was intermediate between the 'Autumn Damask' and the 'Old Blush China' and had been grown in the island for some years under the name 'Rose Edward'. Bréon sent seed of this rose to his friend Jacques, gardener to King Louis-Philippe, and from this seed a rose called 'Rosier de l'Île de Bourbon' was raised. It was distributed in France in 1823 and two years later in England... [The Bourbons] still retain the character of the Old Roses with their strong fragrance, and they still have shrubby growth, but their leaves and stems begin to look more like those of the Hybrid Tea, and they are nearly all repeat flowering.

[From Gardening with Roses, by Judith McKeon, p. 26:] Blooms are typically large, cupped, many-petaled, and very fragrant.

[From Origin of Rose Types, by Roy Shepherd, p. 34:] The classification "Noisette and bourbon" is seemingly unnecessary as both are basically hybrid chinas...

[From The Graham Stuart Thomas Rose Book, p. 131:] The name Bourbon was given to the race because the first plant was a chance seedling found on the Île de Bourbon (Île de Réunion) in 1817, growing in close proximity to both its parents. It became known as 'Rose Edward' in the adjacent island of Mauritius. Seeds were sent to Paris and presumably the best one raised was called 'Le Rosier de l'Île Bourbon'... In its second generation it was named and distributed in France around 1823, reaching England about two years later.

[From Roses: An Illustrated Encyclopaedia..., by Peter Beales, p. 14:] a range of mostly continuously flowering shrub roses which were to adorn gardens worldwide, with very little competition, well into the nineteenth century...

[From The Old Rose Adventurer, p. 519: circa 1844] the Paris garden of [Victor Verdier], celebrated for its fine collection of roses... containing two or three acres... a greater portion of them were Bourbons and hybrid perpetuals... fifteen hundred varieties, selected from above twenty-five hundred cultivated by him since 1827...