This Mexican species, discovered and described in 1942, is known only from a few scattered small stands in the states of Chihuahua, Durango and Nuevo Leon (the last discovered as late as 1981), at about 8,000 ft. Its leading characters are: branchlets glabrous; leaves quadrangular, with some stomata on all sides, more or less two-ranked, stiff and pungently pointed, about [3/4] in. long; cones cylindric, obtuse, chestnut-brown and glossy, 4 to 5[1/2] in. long; scales broadly obovate, [3/4] in. wide at the apex, which is entire.
The Chihuahua spruce is of considerable phytogeographical interest, being probably more closely allied to Asiatic species than to any of North America (and quite distinct from the other Mexican species, for which see under P. engelmannii in this supplement). It is in need of protection, since only in the Nuevo Leon stand does it reproduce itself and if this were to be destroyed its extinction in the wild would only be a matter of time. See further the article by Keith Rushforth in The Kew Magazine, Vol. 3(3), pp. 120-2 (1986). He collected seeds from the Nuevo Leon stand in 1984. The ecology of the Chihuahua spruce is discussed by A. G. Gordon in Ecology, Vol. 49, pp. 880-96 (1968).