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中国丽豆和新疆丽豆是蒙新荒漠两侧豆科植物区系中一对较为重要的间断分布的对子种。中国丽豆分布于黄土高原东部的局部地区，而新疆丽豆分布于新疆塔城一带和西天山山脉。从细胞地理学角度对它们进行了研究，结果表明：中国丽豆为二倍体，核型公式为２ｎ＝２ｘ＝１６＝１２ｍ＋４ｓｍ；新疆丽豆为四倍体，核型公式为２ｎ＝４ｘ＝３２＝２４ｍ（４ＳＡＴ）＋８ｓｍ，两种均为“２Ａ”核型，属的染色体基数ｘ＝８。中国丽豆和新疆丽豆虽然在形态上比较接近，但在核型上的差异明显，应为两个独立的种。中国丽豆是黄土高原比较典型的第三纪古特有种。第三纪末以来亚洲内陆持续旱化、沙漠化和荒漠化不断扩大，这可能是造成其地理残遗的主要因素。而新疆丽豆在倍性上属于比较进化的四倍体，这可能是对其生境变化适应的结果。由于丽豆属在中亚山地集中分布６种１变种，约占全属８种１变种的７７％，因此中亚是本属的现代分布和分化中心。
Rei and Xinjiang Rehmannia are the more important pairs of interdisciplinary distribution of the leguminous flora on both sides of Mengxin Desert. Reid Rehmannia is distributed in the eastern part of the Loess Plateau, while Rehmannia is located in the Tacheng area of Xinjiang and the western Tianshan Mountains. The results showed that the Rehmannia glutinosa Libosch was diploid, the karyotype formula was 2n = 2x = 16 = 12m + 4sm, the Rex Xinjiang was tetraploid, the karyotype formula was 2n = 4x = 32 = 24m (4SAT) + 8sm, both of which are “2A” karyotypes, with a chromosome base x = 8. Although Rex and Rex are relatively similar in morphology, they differ significantly in karyotype and should be two independent species. Chinese Rehmannia is more typical of the Loess Plateau Tertiary. The continuous deepening of inland inland Asia, desertification and desertification since the end of the Third Mdi Period may be the main factors that have caused its geographical remnants. Rehmannia glutinosa Xinjiang belongs to comparatively tetraploidy in ploidy, which may be the result of adaptation to its habitat change. Central Asia is the modern center of distribution and differentiation of genus, because the genus Reiculum distributes 6 species and 1 variety intensively in Central Asia, accounting for 77% of the total 8 species and 1 variety.