Taxation of will-declared trusts: income taxed at ordinary association-of-persons rate, not at maximum marginal rate. Income of a trust declared by will, where it is the only trust so declared, is to be taxed under the special charging rule in the first proviso to section 164(1) rather than at the maximum marginal rate applicable under the general provision for associations of persons; other cases covered by the first provisos to sections 164(1) and 164(3) are likewise not subject to the general maximum-marginal-rate provision and are taxed at the ordinarily applicable association-of-persons rate.