- The club mosses constitute the oldest division within the vascular plant subkingdom. During the Carboniferous era, club mosses were common, often attaining the stature of trees. Today, most species are extinct--including all the larger club mosses--and only about 1,000 species remain. Their simple vascular systems consist of a single vein in each leaf.
- Horsetails also dominated during the Carboniferous, contributing along with club mosses to the fossil fuel stores used today. They also grew tall, but today only the smaller varieties survive, and only about 25 species remain.
- Ferns were the ancestors of today's flowering plants.Jupiterimages/Photos.com/Getty Images
Much more familiar to the average hiker or gardener, ferns are another ancient division in the vascular plant subkingdom that also dominated during the Carboniferous era, when tree ferns adorned the landscape and a few species even developed seeds, another evolutionary leap forward for the plant kingdom. Ferns remained dominant through the Mesozoic era, or Age of the Dinosaurs. Although no seed or tree ferns remain, about 12,000 fern species populate the Earth today. Ferns are the last extant division in the vascular plant subkingdom to reproduce with spores. - The development of the seed was the next major development that helped plants occupy dry habitats by allowing the embryo to remain dormant and protected until ideal conditions encouraged germination. Gymnosperms also use windborne pollen--not water--to carry male sex cells to female plant structures. With the seed ferns extinct, the oldest extant seed plants are the gymnosperms, a group of several plant divisions that produce exposed seeds and woody growth. Gymnosperms include such familiar plants as the conifers, the ginkgo and the tropical cycads.
- Pollinators increase the success rate of flowering plant reproduction.Jupiterimages/Photos.com/Getty Images
The flowering plants or angiosperms are the final division in the vascular plant subkingdom. Today, the flowering plant division is the most abundant and diverse plant division on Earth, consisting of more than a quarter-million species. The flowering plant division encompasses such diverse species as grasses, oak trees, cacti and many aquatic plants. Flowering plants differ from their predecessors because they encase their seeds in maternal tissue, giving them extra protection and, in some cases, giving rise to seed dispersal mechanisms such as fruit or windblown seeds. Some flowering plants produce colorful, scented flowers that attract pollinators that carry pollen from plant to plant in exchange for a meal. - The genus Quercus includes all oak trees.Goodshoot/Goodshoot/Getty Images
Beyond the division level, you can continue classifying vascular plants in increasingly narrow classifications or taxa. For example, flowering plants belong to one of two classes--monocots or dicots--depending on the number of leaves on the embryo. Beyond division and class, plants are grouped in families that share common traits; the legume, pine and rose families are all examples. The genus is the final classification group before the species level and includes very closely related varieties.
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