Petrova N. A. RussiaSaratovSaratov State University, 33 Astrakhanskaya Str., Saratov 410012, Russiakashinas2@yandex.ru Author's articles VITALITY DYNAMICS OF TULIPA GESNERIANA L. (LILIACEAE, LILIOPSIDA) POPULATIONS IN THE LOWER VOLGA REGION AND ADJACENT TERRITORIES