[From The Old Rose Informant, by Brent C. Dickerson, p. 9: in an attempt to devise an accurate system for classifying roses, [in 1820] Jean-Pierre Vibert relied on a long list of criteria, including aspects of the flower, fruit, petals, and prickles, and even then, he found some roses could actually be placed in more than one class. On top of that, there were roses which didn't fit easily into any class --] As to those which I have decided are not appropriate to any of my divisions, I have referred them to the class of Uncertain Hybrids...