Morphological and Chemical Evidence on the Hybrid Nature of Bitter Pecan, Carya x Lecontei

Abstract

In the course of chemical studies on hickory nut oils we noted differences in the fatty acid composition of certain species. To test the usefulness of the data and to clarify the status of a putative hybrid, we chose to examine the morphological and chemical evidence for asserting that Carya X lecontei Little (bitter pecan) is a hybrid between C. illinoinensis (Wangenh.) K. Koch2 (pecan) and C. aquatica (Michx. f.) Nutt. (water hickory). The bitter pecan was first described by Le Conte (1853) as a new species of "Pacane Nut" (Hickorea texana). He compared it to pecan but made no mention of water hickory or suggestion of hybridization. Though Mohr recognized that "crosses between this species [pecan] and the Water Hickory.... are frequently met with" (1889, p. 570), Trelease dismissed these observations with the comment that "I have seen no specimens indicating this hybrid." (1896, p. 34). Based on Le Conte's drawing, Trelease suggested that the bitter pecan was a hybrid between pecan and bitternut (C. cordiformis). Sargent offered no comment on the hybrid nature of bitter pecan when he published detailed descriptions and drawings in The Silva of North America (.1902). It was not until 1937 that Palmer formally recognized bitter pecan as a hybrid between pecan and water hickory. He examined several morphological features and concluded that most of them were intermediate in expression in the bitter pecan. There has been general acceptance of Palmer's findings, though Carya texana (Le Conte) C. DC. has, for nomenclatural reasons, been changed to C. X lecontei (Little 1943). MATERIALS The natural occurrence of bitter pecan is limited to the range of overlap ofthe putative parents (Palmer 1937). According to Little's distribution maps (1949) the contact of pecan and water hickory is extensive in Texas and Louisiana, while