The mode of election, position, rights and authority of an abbess correspond generally with those of an abbot. The office is elective, the choice being by the secret votes of the sisters from their own body. The abbess is solemnly admitted to her office by episcopal benediction, together with the conferring of a staff and pectoral cross, and holds for life, though liable to be deprived for misconduct. The council of Trent fixed the qualifying age at forty, with eight years of profession. Abbesses have a right to demand absolute obedience of their nuns, over whom they exercise discipline, extending even to the power of expulsion, subject, however, to the bishop. As a female an abbess is incapable of performing the spiritual functions of the priesthood belonging to an abbot. She cannot ordain, confer the veil, nor excommunicate. In England abbesses attended ecclesiastical councils, e.g. that of Becanfield in 694, where they signed before the presbyters.
By Celtic usage abbesses presided over joint-houses of monks and nuns. This custom accompanied Celtic monastic missions to France and Spain, and even to Rome itself. At a later period, A.D. 1115, Robert, the founder of Fontevraud Abbey near Chinon and Saumur, France committed the government of the whole order, men as well as women, to a female superior.
In the German Evangelical church the title of abbess (Äbtissin) has in some cases--e.g. Itzehoe--survived to designate the heads of abbeys which since the Protestant Reformation have continued as Stifte, i.e. collegiate foundations, which provide a home and an income for unmarried ladies, generally of noble birth, called canonesses (Kanonissinen) or more usually Stiftsdamen. This office of abbess is of considerable social dignity, and was sometimes filled by princesses of the reigning houses.
Source: An unnamed encyclopedia from a project that puts out-of-copyright texts onto the Internet. This is from a very old source, and reflects the thinking of about 1900 in the UK. -- BryceHarrington -- Jason Scribner