SPJUT, RICHARD W. World Botanical Associates, P.O. Box 2829, Laurel, MD 20709-0829. - A phytogeographical analysis and classification of leaf characteristics of Taxus (Taxaceae).
A phytogeographical analysis of leaf character data will be presented
to show that Taxus is least variable in North America and NW
Himalayas, and most diverse in SW China. Characters include the number
of cells across a marginal zone without papillae, and number of
stomata rows/band. Leaf characteristics will be discussed for three
species groups typified by T. baccata, T. wallichiana, and T
sumatrana, and their subdivisions. Most European specimens have a
baccata type (8-10 stomata rows/band bordered by a marginal
zone of 4-7 smooth cells followed by 7-22 papillose cells), and less
often a canadensis type (4-9 stomata rows/band bordered by 8-24
smooth cells and 0-12 papillose cells); the latter includes a
cuspidata subtype that differs by papillose cell walls.
Specimens from E Asia have the canadensis and cuspidata
types, but often with more stomata, which range from 7-13(-16)
rows/band. Northwest Himalayan specimens have the baccata type
with 5-9 stomata rows/band, and show less variation in leaf length and
phyllotaxy. All three types occur in the Caucasus Mountains, but most
specimens there appear similar to those in Europe. From the E
Himalayas to SW China, and in North America, occurs the
Wallichiana Group. Its leaves usually have a uniformly
papillose undersurface with a relatively narrow marginal border of
smooth cells, 0-7 (-10) cells across. The epidermal cells are
distinctly angular in transverse sections, and stomata show
geographical differences, 7-21 rows/band in Asia, and 4-11 rows/band
in North America. A Chinensis Subgroup, mostly in central
China, Indonesia and Philippines, differs by rounded epidermal cells
(x-sect.) that are sometimes less papillose on the ventral midrib. The
Sumatrana Group, which is common in SE China, especially below
2,000 m, has a broad margin of cells bordering stomata bands, from
8-36 cells across, and often a truncate midrib.
Key words: leaf anatomy, leaf morphology and taxonomy of Taxus, phytogeography, Taxaceae