Royal Order of Scotland: This is a Masonic Order which until relatively recent times was confined to the Kingdom of Scotland, and which (in the US and Scotland) only admits Master Masons who have received the Royal Arch Degree. (in the US, part of the YORK RITE) It consists of two degrees, namely, that of H. R. D. M. and R. S. Y. C. S., or, in full, Heredom and Rosy Cross. The first may be briefly described as a Christianized form of another Masonic degree, with references and influences from the Culdees, who introduced Christianity into Scotland in the early centuries of the church. The Second Degree is an Order of Chivalry or at least Civil Knighthood, as is supposed to have been founded in 1314, by Robert Bruce after the battle of Bannockburn, and conferred by him upon certain Masons who had assisted him on that memorable occasion. He, so the tradition goes, gave power to the Grand Master of the Order for the time being to confer this honor, which is not inherent in general body itself, but is specially given to the Grand Master and his Deputy; and which can be conferred only by them, or those Provincial Grand Masters appointed by them. The number of knights is limited, and formerly only sixty-three could be appointed, and they Scotsmen; now, however, that number has been much increased, and distinguished Masons of all countries are admitted to its ranks.

extracted from Mackey's 'Encyclopedia of Freemasonry'

words in italics have been paraphrased