The first three degrees in Masonry, Entered Apprentice (1°), Fellow Craft(2°) and Master Mason (3°) are all conferred in a Blue Lodge, under the authority of the Grand Lodges. This is recognized as the unquestioned prerogative of the Grand Lodge. In Texas, where the Valley of Galveston is located, no Mason may petition any appendant body, including the Scottish Rite, unless they have made satisfactory proficiency in the examination of a Master Mason.
At all times the Scottish Rite recognizes the supreme authority in Masonry of the Grand Lodge and the Grand Master. It teaches that there is no rank higher than that of Master Mason, and no Masonic symbol more significant than the Master's Apron, but it elaborates and emphasizes the great principles enshrined in Craft Masonry.
When a Master Mason advances to the higher degrees of the Rite, it does not detract but adds to his interest in everything for which the Blue Lodge stands. The Scottish Rite aids, supplements and reinforces the Blue Lodge in every way. As organizations these bodies are mutually dependent and strengthen each other with reciprocity.
-Parts of this description were taken from
"Scottish Rite Relationship to Blue Lodge Masonry"
Saint Vrain Masonic Lodge #23, Longmont, Colorado
October 13, 2009