What does LATEH2 stand for?

Lappula texana (Scheele) Britt. var. homosperma (A. Nels.) A. Nels. & J. F. Macbr. - Scientific name - Accepted name: Lappula occidentalis var. cupulata - Family: Boraginaceae - USDA National Plant Data Center symbol - Botany - Taxonomy (USDA)