The Director of Public Works is hereby authorized and empowered to issue permits for the maintenance of sidewalk flower-vending stands at the locations specified in Section 155 of this Article, subject to the proviso contained in said Section 155. In considering the issuance of sidewalk flower-vending stand permits and in prescribing the location of such stands within the areas set forth in Section 155 of this Article, the Director of Public Works shall give due regard to the conveniences and necessities of the owners, occupants or tenants of offices, stores or shops in the vicinity.