Section 3. Seven or more persons, residents of the commonwealth, may associate themselves as a corporation, association, society, company or exchange, to conduct within the commonwealth any agricultural, dairy or mercantile business on the co-operative plan. The word ”co-operative” shall form a part of the name of the corporation, and, for the purposes of this and sections three A to nine, inclusive, the words ”association”, ”company”, ”exchange”, ”society” and ”union”, shall have the same signification and shall import a corporation. The corporation shall be formed as provided in chapter one hundred and fifty-six B, with shares having par value, and shall be subject to the provisions thereof so far as consistent with said sections.