keys to the vascular plants of east texas - Botanical Research ...

DIVISION PINOPHYTA
CONIFERS
CUPRESSACEAE 391
AThis is the gymnosperm division with the largest number of living representatives (68 genera
and 629 species arranged in 8 families—Farjon 1998). The seeds are typically borne in cones,
hence the common name, CONIFERS, from Latin conus, cone, and -fero, bearing. The Pinophyta is
sometimes referred to as the Coniferophyta (Raven et al. 1986). Recent molecular evidence
(Stefanovic et al. 1998) supports the theory that the conifers are a monophyletic group. The fossil
history of the conifers extends to late in the Carboniferous Period (360–286 million years
ago). Vast forests of Pinophyta (PINE, SPRUCE, FIR, DOUGLAS-FIR, CEDAR, etc.) are present across the
northern part of the world between areas of tundra and deciduous forest; they dominate the
biome known as taiga. These mostly evergreen species have xerophytically adapted, desiccation
resistant foliage that allows them to maintain photosynthesis through the long winter and
make immediate and maximum use of the short growing season available in the taiga. The
leaves last for several years, which means that the high nutrient demand associated with making
a new set of leaves each spring is avoided—this is considered a significant advantage on the
generally nutrient-poor soils of the taiga (Pielou 1988). The result is that this is one of the few
gymnosperm groups that has maintained dominance over flowering plants across vast areas.
Though not native to TX, the small conifer family Taxaceae (YEWS) is important because the
bark of Taxus brevifolia Nutt. (PACIFIC YEW, CALIFORNIA YEW) is the source of the terpenoid
taxol, a mitotic (= cell division) inhibitor, which is an anti-cancer drug used in the treatment of
ovarian, breast, and other types of cancer. As a result of this use, PACIFIC YEW populations in
some areas have been greatly reduced. While not important as a direct source of taxol, the
leaves of the European and Mediterranean Taxus baccata L. (EUROPEAN YEW, ENGLISH YEW) contain
a compound that is now being used in taxol synthesis. It is interesting to note that like
many medically valuable plants “discovered” by modern medicine, Taxus has a long history of
medicinal use; e.g., early Europeans used it in treating hydrophobia (=rabies) and heart ailments,
and Native Americans used it against such conditions as rheumatism, bronchitis, fever,
scurvy, and skin cancer. � Also like many medicinal plants, YEWS can be fatally poisonous to
humans and animals. Taxus species have long been used in various ways such as in arrow poisons,
to kill fish, and in murder and suicide. Death from YEW can be sudden, with animals
sometimes being found close to the plant with foliage still in their mouths (Kingsbury 1964;
Hartzell 1991, 1995; USDA Forest Service 1993; Cragg et al. 1995; Suffness & Wall 1995; Burrows
& Tyrl 2001).
REFERENCES: Hardin 1971; Bell & Woodcock 1983; Raven et al. 1986; Bold et al. 1987; Hart 1987;
Eckenwalder 1993; Woodland 1997; Farjon 1998; Stefanovic et al. 1998.
CUPRESSACEAE Rich. ex Bartl.
CYPRESS OR REDWOOD FAMILY
Evergreen or deciduous trees or shrubs; monoecious or in Juniperus usually dioecious; leaves
variously opposite, whorled, or alternate and spirally arranged, sometimes appearing 2-ranked
due to twisting, sometimes dimorphic, sometimes with an abaxial resin gland; pollen cones
usually solitary, terminal; pollen not winged; seed cones with scales fleshy or woody.
AThis family has often been divided into Cupressaceae (in the strict sense), for those genera
having opposite or whorled leaves (including Juniperus), and Taxodiaceae or REDWOOD FAMILY,
for those genera having leaves mostly alternate. We follow Eckenwalder (1976), Hart and Price
(1990), and Watson and Eckenwalder (1993) in treating them as a single family. Molecular evidence
(Brunsfeld et al. 1994) shows Cupressaceae (in the strict sense) derived from within
Taxodiaceae, supporting the single family treatment. The family is widespread in temperate areas