Section 91. No person within the commonwealth shall detach, alter, deface or destroy any label provided for in said sections eighty-four to one hundred and one, inclusive, or the regulations promulgated thereunder; nor alter or substitute seed, in a manner that may defeat the purpose of said sections; nor disseminate any false or misleading advertisement concerning agricultural, vegetable, flower or tree and shrub seed; nor hinder or obstruct any authorized person in the performance of his duties under said sections eighty-four to one hundred and one, inclusive; nor fail to comply with an official order to withhold from sale certain seeds as provided in section ninety-five; nor move or otherwise handle or dispose of any lot of seed held under a ''stop-sale'' order or tags attached thereto, except with the written permission of the enforcing officer, and for the purpose specified therein.

No person shall sell, offer or expose for sale any color mixture of a single kind of flower seed representing four or more colors or shades, in which any one color or shade occurs in sixty per cent or more of the plants which the mixture is capable of producing, unless colors or shades and approximate percentage of each is indicated on the label, or sell, offer or expose for sale a mixture of flower seed kinds in which any one kind is present in excess of twenty-five per cent by seed count unless the kinds present and the approximate percentage of each are indicated on the label.