Grasses and wildflowers (forbs) are herbaceous (non-woody) plants, which means that the stems are typically green, relatively soft, and fibrous. Both herbaceous and woody plants are angiosperms (flowering plants). The subphylum of angiosperms includes all plants that reproduce by seeds, and these seeds are contained within an ovary, or fruit. There are two main classes of angiosperms; monocotyledons (monocots) and dicotyledons (dicots). All grasses are monocotyledonous, meaning that within their fruit they have only a single cotyledon (seed leaf) per seed. Most of the wildflowers are dicotyledonous, meaning that they have two cotyledons per seed, and their flowers usually have four or five parts.
Angiosperms reproduce themselves through seeds. To produce this seed the parent and the progeny both have cells with two sets of chromosomes. These are then designated as diploid cells or as having a chromosome number (ploidy) of 2n. During sexual reproduction one set of chromosomes is provided by the female through the egg cell (ovule) and one set of chromosomes is provided by the male through the sperm (pollen). The ovule and the pollen are both haploid cells, in other words, they have a ploidy of n. To produce a new generation of individuals (from seeds) flowering plants undergo a process called double fertilization.
Double fertilization occurs in the embryo sac within the ovary (fruit) of the female flower parts. The first fertilization involves the fusion of the first pollen nucleus (n) with the one ovule nucleus (n) to form the zygote (n+n=2n), the new diploid generation. The second step in this fertilization involves the fusion of the second pollen nucleus (n) with two haploid polar nuclei (n+n) to form the triploid (3n) primary endosperm nucleus.
The zygote divides repeatedly forming the embryo which continues to develop to maturity. The endosperm nucleus divides forming the endosperm, a nutritive tissue of the seed. Variation in seed development has resulted in two categories of seeds. Embryo development can occur at the expense of the endosperm, no endosperm remains once the seed grows to a seedling. This type of development occurs in the non-endospermous seed category. The food reserve for the new seedling in such seeds is located in the fleshy cotyledons which are part of the embryo. In comparison there is the development in which both the endosperm and the embryo develop within the seed to maturity. This occurs in the endospermous seed category where the major food reserve for the new seedling is stored in the endosperm. In these cases the cotyledon(s) serve as a food absorbing organ during early seedling growth (Figure 2.11).
The embryo, composed of plumule (shoot rudiment), radicle (root rudiment) and cotyledons (food supply), grows into a seedling after germination (Figure 2.11). Germination, by definition, is the beginning or continuation trigger for the growth of a seed, involving the initial uptake of water. A seed is considered to have germinated when the radicle emerges from the swollen seed coat (testa).
There are two main types or germination, epigeous and hypogeous. In a plant exhibiting epigeous germination the cotyledon(s) is carried above the soil level; in a plant exhibiting hypogeous germination the cotyledon(s) remains below the soil level.
During early seedling growth, the root and the shoot systems form before the plant has become a complete, photosynthetic autotroph. During this time, large amounts of oxygen are required for respiration. Nitrogen also is needed in large amounts for the formation of new cells and tissues.
Carbon and nitrogen reserves in seeds are stored as starch, fat and protein molecules either within the endosperm or the cotyledon, depending on the species. The starch, fat and protein molecules are each polymers which are then broken down into the smaller molecules of simple sugars, fatty acids and amino acids, respectively. The fact that these are stored in more complex forms first is because the larger structures are easier for the plant to transport between cells.
Starch is a polymer of glucose (sugar) molecules. During germination it is broken down in a series of steps an in this simplified form, the sugar is utilized by the growing embryo. The way the starch is transformed into glucose is fairly straight forward. After the initial germination, a growth regulator is released by the embryo. The starch becomes hydrolyzed by the action of these enzymes, and the end product (glucose) is reabsorbed by the scutellum and transported to the developing embryo where they are metabolized.
Fats and fatty acids contain large numbers of carbon-hydrogen bonds, and so they release energy when they are broken down during development. However given this, most fats are used for the storage of the energy from sugars as cells can easily synthesize fats from sugars. Fatty acids also are an essential barrier against moisture loss from within the cell.
Proteins are polymers of amino acids. They are essential because they provide a source of amino acids which are indispensable in the development of the structural materials and enzymes needed in seedling growth.
The embryo of a germinated seed grows into a seedling. The seedling, though comparatively small, does exhibit the two major systems seen in a mature plant, namely, the root and shoot systems (Figure 2.11).
The primary root results from the growth of the radicle in the seeds. Branch or lateral roots later develop from the primary root. Lateral roots may have their own laterals, etc. Adventitious roots are roots which arise from any plant part other than a root (for example from leaves, stems, petioles, etc.). The tap root is the central root, usually developing from the primary root, from which grow the lateral roots. Not all plants have tap roots. The other main type of root system is the fibrous root system, where the lateral roots grow from the adventitious roots. Most grasses have fibrous root systems.
A leaf (Figure 2.12) in dicotyledonous (two cotyledons) plants may have stipules, often a petiole (leaf stalk), and always a lamina (blade). A leaf is always attached to the stem at a node, creating the joint where the buds are produced. A leaf may or may not have a stalk. If the blade is one entire structure, it is a simple blade therefore the leaf is a simple leaf. If the blade is subdivided into smaller portions, the leaf is a compound leaf, each subdivision being a leaflet. Leaves or parts thereof may become modified into tendrils. A tendril is modified into a slender coiling structure which functions to aid in support.
The blade or lamina is the broad expanded part of a leaf or leaflet. A leaf in the grasses has a blade and a sheath. One or more sheaths may act as the outer wrapping of the stem (Figure 2.13). Grasses are among the many different plants belonging to the monocotyledonous (one cotyledon) plants. Some monocotyledonous plants have leaves with a stipule and/or a petiole.
The upper angle formed between the petiole and the stem is the leaf axil. There often is an axillary bud in the axil of the leaf. An axillary bud will grow to produce a lateral branch or it may modify to create a stolon, rhizome, thorn, tendril, flower or inflorescence.
A node is the place on a stem from where a leaf arises. The node occupies the entire cross section of the stem. The first node is exactly at the point of attachment of the cotyledon(s) to the stem. The internode is the length of stem between two nodes. The first internode is the stem between the first and second nodes. This internode is called the epicotyl, literally meaning above the cotyledons. The hypocotyl is the stem segment below the cotyledons. At one end (upper end) of the hypocotyl is the first node, at the other end (lower) is the root/stem junction. In some plants, the hypocotyl does not elongate with growth.
Grasses, in particular, consist of stems called culms, which are composed of nodes and internodal areas. 
The leaves are borne in two rows or ranks alternating along the culm at the nodes (Figure 2.13). Leaves of grasses are composed of three principle parts (Figure 2.14): a tubular sheath which surrounds the culm and commonly has overlapping margins; the blade, which is usually narrow, elongated, and with parallel veins; and the ligule, a thin membrane or row of hairs at the juncture of the sheath and blade in the side facing the stem.
After the development of the stem and the leaves, the plant matures an develops a flower (or inflorescence) and then a fruit. Figure 2.15 shows the comparison between a flowering branch and a grass spikelet. This illustrates the similarities and helps to visualize how grasses get classified as having flowers, even though they don't have petals. Grass flowers are typically very small and inconspicuous.
All flowers have the same basic structure, using they same types of reproductive organs (Figure 2.16). There is the stamen, composed of the anther and filament, which produces the male reproductive nuclei, the pollen. Along side of this is the pistil, composed of the stigma, style, and ovary, which produces the female reproductive nuclei, the ovule. At the base of the flower is where the sepal ( regular flower) or lodicule (grass flower) is found. The lodicule works similarly to the sepal; when the time comes to bloom, they swell up and force the flower open. Figure 2.17 compares the two flower structures. Where the flower has petals to surround and protect itself, the grass has the palea and lemma to protect it. This entire structure then is called the floret.
When identifying a plant by it's inflorescence, it is important to know the different forms the flower arrangements can take (Figure 2.18).
Grasses only display the first three forms of inflorescence; the panicle, spike and raceme arrangements. Usually the palea and lemma are still so close together that the flower is not visible.
As the plant matures the ovary ripens producing the grain or fruit. However, in most grasses, when the grain is ripe it comes off the plant with the palea and lemma still intact, surrounding the seed. This is then called the chaff and pappus, which needs to be cleaned off. There are as many different types of fruit as there are flowers, each ovary matures differently.
