B. Papp szerk.: Studia Botanica Hungarica 34. 2003 (Budapest, 2003)

Debreczy, Zsolt; Rácz, István: A re-assessment of the new taxa of firs (Abies Mill.) reported from Mexico in 1995

Name: viridulus, viridula (Lat. adj.) meaning greenish, refers to the colour of the foliage, markedly distinguishes this geographically isolated variety from the northern type with grey, pruinose needles. Discussion: Abies lowiana has not been distinguished and recorded in Mexico so far. The species, mistakenly considered as a variety of A. concolor (A. c. var. lowiana (Gord.) Lemm.), should be considered as the "continental vicariant" of the Pacific species A. grandis. It is easy to separate it from A. concolor in the strict sense even by some prominent, easily available, outer morphological characters: in A. lowiana the shade branches and branchiets are rough and hairy (not smooth and glabrous), the winter branchiets are brownish yellow (not greenish grey or grey); the leaves, positioned in regular helical order are evenly spreadout to a horizontal position appearing "dichotomous" or "pectinate" on sterile, or pectinately upcurving in right angle to both sides of the branchlet on fertile shoots (not diverging in all directions according to the helical order and often curving back- and forward when in upper position). On primary terminal shoots, "leaders", the leaves are abruptly upcurving to parallel the shoot such as in A. grandis (not spreading or ascending up to 45°). They are 3-5 cm long, rounded at apex on regular shoots (not up to 10 cm or more, acute and abruptly pointed); the stomata arranged in two silvery stripes below, with up to 9 stomatophorus lines in each and in a defined central stomatophorus band near the central longitudinal grove above the midvein with up to 11 lines (not evenly spread on both sides); in cross section the shade leaves are elliptical (not rectilinear); the cones of A. lowiana are typically conspicuously uneven in outline, light reddish brown, rarely green (not more or less even in outline, purplish, less often green). The variety (var. viridula) differs from the northern type by having less pruinose leaves above and shiny green leaves below. This could be a result of the ecological differences in the habitat of the two plants: such as the canyon environment with shorter dormancy period in the southern type, while exposed high mountain slopes with long winter and hot, dry summer in the northern one. Discovery: the species, represented here by the variety, is found in a canyon north of Madera, Chihuahua. We saw several specimens in the shady north-northeastern side of the wide valley about 10 km northeast of Madera, Chihuahua at an altitude of about 2,700 m. We visited this site on May 4, 1994 and found the tree with well developed female and male cone-inflorescences (strobiles). We asked the help of Mr Leonel Iglesias Quitierrez, Director Forestal NC Chihuahua, Chihuahua, and M. C. Raul Narvaez Flores, Jefe del Campo Experimental Madera, associates of INIFAP (Instituto Nacional de Investigaciones Forestales y Agropecuarias), CIR (Centros de Investigación Regional del INIFAP) Noroeste to make this exploration possible. The trees formed a mixed stand with Pseudotsuga men-