14 at Kilmainham, Kent in Cork, Casement in England.

May 3rd 1916        Kilmainham Gaol        
Pádraic Pearse
Thomas Clarke
Thomas MacDonagh

May 4th 1916        Kilmainham Gaol        
Joseph Plunkett
Edward Daly
Michael O'Hanrahan
Willie Pearse

May 5th 1916        Kilmainham Gaol        
John MacBride

May 8th 1916        Kilmainham Gaol        
Eamonn Ceantt
Michael Mallin
Sean Heuston
Con Colbert

May 9th 1916        Cork Detention Barracks        
Thomas Kent

May 12th 1916        Kilmainham Gaol        
Seán MacDiarmada
James Connolly

August 3rd 1916        Pentonville Prison, London        
Sir Roger Casement

Treason was one of the charges in the drumhead court martials. The video here should contain a reading including the charges.