Some of this information goes back to Graham (1960) working on the introgression of P. glandulosa in Tamaulipas and Texas, but has been poorly followed up. See Earl (1998). Graham had the invader P. microphylla von Humboldt, Bonpland & Kunth from south of the Neovolcanic axis as in the western Balsas valley. Graham also had trees of the T113 type (Table 1), a microphyllan derivative from Mina, Nuevo León (NL). T113 is a microphyllan invader from Ciudad Victoria, Tamaulipas, now back crossing long leaflet natives in NL. In Mina, NL, it is at the 113 km highway marker from Monterrey, NL on the road to Monclova, Coahuila.