When people think of Gallicas ‘Apothecary’s Rose’ or ‘Rosa Mundi’ usually come to mind.
[From Roses, by Susan Bales, p. 50:] the earliest recorded roses cultivated in Europe. Fragrant with the scent known as the true old rose perfume. Once-blooming in midseason. Their flowers are flat in pink, purple and maroon, some with crimson shadings - low growing, rounded and neat - suckering roses, they spread by underground runners. Most Gallicas are winter hardy and more adaptable to poorer soils than other roses.
[From The Glory of Roses, by Allen Lacy, p. 81:] Linnaeus named one rose commonly grown in Europe 'Rosa gallica' - the French or Gallic rose ... its original habitat was far more likely to have been in eastern Europe or Asia Minor. Furthermore, long before Linnaeus this species had evolved into several distinct forms in gardens, differing in degree of fragrance, plant habit, and the color and number of petals.
[From A Little Book of Roses, by Hazel Le Rougetel, p. 8:] In 1846 a leading American rose grower, William Prince, of Flushing, New York listed 93 "striped, variegated, mottled or marbled" Gallicas. Comparatively few endured... The majority of variegated Gallicas are double.
[From Landscaping with Antique Roses, by Liz Druit and Michael Shoup, p. 129:] Of all the old garden roses, only Gallicas are truly purple - it is a habit of this class to assume some shade of greyish-purple as the flowers fade.
[From The Rose Bible, by Rayford Reddell, p. ?:] The oldest of all Antique garden roses; they are also the most highly developed (only about 50 hybrids are now in general cultivation, but there once were more than 900 named varieties)... Gallicas figure prominently in the ancestry of the other four classes of Antique Roses ... Although there are a few soft pinks, most Gallicas blossom in strong colors - deep pink, purple, violet, and mauve, with crimson shadings in between. Many varieties are dramatically striped or mottled; almost all are fragrant.
[From The Old Rose Advisor, by Brent Dickerson, p. 112: Dickerson suggests that many gallicas are Hybrid Chinas or Hybrid Bourbons in disguise,] non-remontant offspring generated in Hybrid Perpetual breeding. They differ from the French Roses in their growth, which is more diffuse; in their foliage, which is usually smooth, shining more or less, and retained on the tree later in the year, in their thorns, which are larger, and usually more numerous; and in their flowers, which are produced in large clusters, whose petals are less flaccid, and which remain in a perfect state a longer time after expansion.
[From The Rose, newsletter of the Royal National Rose Society (RNRS) Historic Rose Group - No. 10 Autumn 1995 - p. 4:] At the International Historic Rose Group weekend at St. Albans 23-25 June 1995 Prof. Francois Joyaux (University of Paris) lectured on the development of Gallica hybrids in France in the first half of the 19th Century, largely brought about out of necessity because the Continental blockade during the Napoleonic Wars. Of the 650 varieties of Gallicas listed by Gravereaux, founder of the Roseraie de l’Hay in 1912 (108 of them bred during the Napoleonic Empire) only about 250 remain.
[From The Complete Book of Roses, edited by John Mattock, p. 99:] Until the introduction of the new breeding lines from the Far East, this was without doubt the most popular type of rose grown throughout the Western world... A characterisitc of this group is the proliferation of striped varieties.
[From Landscaping with Antique Roses, by Liz Druitt and Michael Shoup, p. 104:] The varieties of garden roses that the Romans grew and that continued to be grown in Europe were almost certainly hybrids of Rosa gallica, whose Latin name means "rose of the Gauls" (the inhabitants of what is now France) but whose physical roots can be traced at least to Persia in 1200 BC.
[From Peter Schneider on Roses, by Peter Schneider, p. 114:] Gallicas had their heyday in the first four decades of the nineteenth century, before the newly imported, repeat-blooming China roses mated with then and wiped them out. Very few gallicas were introduced after the 1840s, although on, 'Marcel Bourgouin', appeared as late as 1899... prone to mildew... fragrant... this fragrance actually increases when their petals are dried...
In addition to the books listed above, you can find further information about gallica roses in:
Rosa Gallica, by Suzanne Verrier
La Rose de France, by Francois Joyaux