All tenants of joint estates except those holding in entirety 72 may convey all or part of their interests to a stranger without the consent of their co-tenants.73 But they cannot, by such conveyance, pass a valid title to any separate part of the common property.74 So a tenant of a joint estate cannot dedicate land to the public for a street.75 It has already been said that one joint tenant, by conveying to a stranger, severs the joint tenancy,76 but such a tenant cannot devise his share, unless he be the last survivor.77 A co-parcener may pass his interests by devise.78