Monographs Details: Cercis canadensis var. texensis (S.Watson) M.Hopkins
Authority: Isley, Duane. 1975. Leguminosae of the United States: II. Subfamily Caesalpinioideae. Mem. New York Bot. Gard. 25 (2): 1-228.
Description:Distribution and Ecology - Nc Texas slightly into s Oklahoma, w to Trans-Pecos Texas. Rocky limestone soils primarily of Edwards Plateau and ne; ravines, hills, often with Quercus and Juníperas, occasionally cult. March-April. Mexico.
Discussion:C. reniformis Engl, ex Wats. (1882)
C. occidentalis auct. p.p.
Cory and Parks (1937) regarded xeric Cercis in Texas as C. occidentalis rather than C. canadensis. Hopkins (1942) related it instead to the eastern species, and he and subsequent Texas authors (Turner, 1959; Correll and Johnston, 1970) recognized two varieties of coriaceous-leaved Cercis. Ostensibly, these writers agree in segregating var. mexicana from var. texensis on the basis of the velutinous twigs and under surfaces of the leaves. There, congruence ends. Hopkins (1942) rigorously adheres to absence or presence of pubescence, and since pubescent phenotypes may be found almost throughout Texas, his varieties are largely sympatric. Contrariwise, Turner (1959), followed by Correll and Johnston (1970), limited var. mexicana to Trans-Pecos Texas, making the taxa essentially allopatric.
While I have taken up the delimitation of these Texas authors, I disagree with Turner’s (1959) statement that vars. texensis and mexicana are as distinct from each other as from var. canadensis. Indeed, when two competent taxonomists as Turner and Hopkins come to such disparate conclusions regarding the delimitation of var. mexicana, the possibility arises that they are battling with an immaterial ghost.
Xeric Cercis in west Texas and immediately adjoining Mexico is consistently pubescent, even velutinous, on under-leaf surfaces. Elsewhere it is ideally and frequently a plant with small, coriaceous, shiny, glabrous leaves. However, plants with puberulent to almost velutinous blades are of sporadic occurrence as far east as Dallas Co. and are locally common on the Edwards plateau. Some from north-central Texas possess large leaves (to 10 cm) with a tendency to acute or acuminate apices. In northeast Texas, this could reasonably be attributed to genetic influence of contiguous var. canadensis, but such also occur in Mexico. Pubescence may be associated with either the small circular leaf form or the larger acuminate one and the interdigitation of these in Mexico complicates the picture to the degree that var. mexicana might be regarded as but a local form of a regionally diverse complex.
Distribution:Mexico North America
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