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Class:
Pinopsida
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Pinales
(Coniferales)
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Taxales
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Cupressaceae
(Cypress)
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Taxaceae
(Yews)
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Pinaceae
(Pines)
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Division:
Coniferophyta
These
are trees or shrubs which reproduce by seeds (matured ovules). They increase
in diameter by a cambium layer which produces xylem (woody tissue which makes
up most of a tree trunk, which conducts water from the roots to the leaves)
toward the inside and phloem (commonly called the bark, which conducts food
manufactured by the leaves to the roots) to the outside, and thus have true,
well-developed secondary growth. Secondary growth is composed of any cells
produced by cell divisions in the original growth which is referred to as
primary growth.
Pollen is produced in separate small male cones from the larger female cones
which produce ovules. Ovules are produced naked on the adaxial (toward the
main axis) surface of cone scales. The Division Pinophyta has no ovaries.
The Division Pinophyta differs from flowering plant division (Magnoliophyta)
in that there is no container or ovary surrounding the ovules and thus produces
no true fruit (fruits are matured ovaries). Pollination occurs by wind transfer
of the pollen from pollen producing cones to the seed cones. The pollen lands
on a droplet on the micropyle (micro=small; pyle=opening); opening of the
female gametophyte). The female gametophyte is haploid, thus its nuclei contains
only half as many chromosomes as the rest of the cells in the tree. It is
multicellular and produces archegonia (The organ in which the female sex cells
are produced). The seeds of the Pinophyta contain no endosperm as in the Magnoliophyta.
The food reserves for the developing embryo are stored in the tissue of the
female gametophyte. The sporophyte (2n generation) is the dominant and obvious,
independent generation. The sporophyte has simple leaves which are usually
needle-like and small. The vascular system of the leaves consists mainly of
a midvein. The veins do not form an anastomosing (closed network) vascular
system.
Class:
Pinales
(Coniferales)
The conifers found in Idaho are monoecious (both sexes on one plant specimen)
or dioecious (Pollen producing cones only on one plant and seed producing
cones on different plants–e.g. Taxaceae) trees or shrubs (trees and shrubs
are perennials because above ground parts remain alive year after year) with
either scale-like or needle-like simple leaves. Most of ours are evergreen,
but one species (the larch or tamarack) is deciduous. Reproduction structures
are in cones (strobili) rather than flowers. Thus there is no calyx, no corolla,
and no pistil. The several stamens are spirally arranged in small, deciduous
strobili (fall off after pollen is shed). The stamens are on the abaxial (side
away from the main cone axis) surface of the cone scales. Each stamen has
two or more anther sacs. There is one ovule in the Taxaceae cones, but the
rest have 2 to many which are produced in pairs on the adaxial surface of
spirally arranged scales in woody cones e.g., hemlocks [Taxaceae], pines,
spruces, firs, douglas firs [Pinaceae] or fleshy cones in the junipers, arborvitaes
[Cupressaceae]. The matured ovules (seeds) tend to be large and contain abundant
food reserves. Most species have two ovules or seeds born in pits near the
base of each scale but a few have several. Several have winged seeds. The
embryo has two to several cotyledons. Seeds are dispersed by shrinkage of
the cones which allows seeds to fall out, by cones disintegrating, or by serotinous
cones which are opened by animals, decay, or by fire.
Class:
Taxales
This class contains only one family, the Taxaceae. Thus the description of
the class Taxopsida and family Taxaceae are the same. They are commonly dioecious
(but can be monoecious) evergreen trees and shrubs which have no resin canals.
The branches tend to spread or droop. The spirally arranged, linear, need-like
leaves sometimes appear to be in two ranks. The pollen is produced in small
cones whose scales bear 2-8 pollen sacs. The ovules is solitary in a small
cone which has 2 pairs of bracts. At maturity, a red aril almost completely
surrounds the black seed which can be seen from the distal end. The final
result does not appear to be a cone, but appears to be a berry. Differing
from the Pinaceae cleavage embryony does not occur in the Taxaceae. The fleshy,
red aril is edible, but the black, shiny seed is poisonous to mammals, including
Homo sapiens. The hard, durable, attractive wood has been and is still used
for making bows.