"noxious weed" means weed species declared noxious by the Noxious Weeds Act; Cap. 231 "off-type plant" means a plant which does not exhibit the recognised and accepted habits and characteristics of the cultivar being grown; "purity" means the percentage by weight of pure seed as determined by purity analysis; "seed certification" means a system for quality control of seed multiplication and production; "seed class" means a stage in a seed multiplication system well defined in respect of parent seed, standard of cultivation and seed quality; "seed lot" means a specified quantity of seed, which is homogeneous and physically identifiable; "S.C.C.I." means the Seed Control and Certification Institute of Zambia; "variety" means cultivar; "weed plant" is any plant which is not of the same species as the crop being grown, and which is generally considered as a weed. 3. The seeds set out in the First Schedule shall be prescribed seed for the purposes of the Act. Prescribed seeds 4. The Seed Control and Certification Institute of Zambia established under section seventeen is an official seed-testing station. The Seed Control and Certification Institute of Zambia 5. (1) No seed shall be offered for sale unless it has been certified or it Sale of Seed has had its quality declared under regulation 7.