Abstract
The two species of Arctium grow in Kazakhstan: Arctium leiospermum Juz. et Serg. (AL) and Arctium tomentosum Mill. (AT). Only the roots of AT are used in medicine. The objective is to study the leaves and roots of the AL as a medicinal plant material. A comparative study of the AL and AT leaves and roots showed the presence of distinctive characteristics: AL leaves: almost naked, the bottom is slightly hairy; AT leaves: green above, tomentose below; AL baskets: green, glabrous, rarely purple, sitting on a short, 1–3cm long, peduncles, involucre leaves all end with a hook; AT baskets: hairy, sitting at a long peduncles, inner leaves, involucre with a small cusp planted, but no hook-curved. Anatomical structure of AL leaves is also different from the structure of the AT leaves. AT leaves: epidermal cells are not elongated, less sinuous walls, much mechanical tissue. AL leaves: epidermal cells are elongated, with very sinuous walls, a little mechanical tissue. These is no significant difference in morphological and anatomical structure of AL and AT roots. Content of biologically active substances in AL roots is 5–10% higher than in AT roots.