Special meetings may at any time be called by the trustees for the transaction of any business specified in the warning of said meeting. The trustees shall call a special meeting upon written application and petition of not less than five percent of the qualified voters of said corporation stating the purpose for which they wish it called. When the office of any one or more of the trustees is vacant, the remaining trustees may call meetings. When there is no trustee who may call meetings, they may be called by the Clerk.