The Flora Connection

The plant kingdom is one of the oldest categories of living organisms. Evolved from primitive algae in the seas of a very young planet Earth more than 550 millions years ago, many plants today are still aquatic, although most now live on land.

More than 250 000 plant species exist and, as you can imagine, botanists have classified them into many different groups. The principal distinction in plant classification is based on the way plants absorb water. The more primitive plant forms absorb water through their surface: these are called non- vascular plants. More evolved plant forms have tube-like structures which transport water from the roots to the stems and leaves: these are called vascular plants.

Non-vascular plants are represented by the Bryophyte. They are small plants often living in dense colonies and include mosses and liverworts.

Vascular plants are separated in two divisions: the Pteridophyte and the Spermatophyte. Pteridophyte have, like Bryophyte, a reproductive cycle involving spores rather than seeds. Numbering around 10 000 species today, they thrived in greater numbers during the Carboniferous period around 300 million years ago. They include ferns and horsetails.

Spermatophyte have a reproductive cycle which develops pollen that results in seeds containing the embryo of a new plant. They are divided into two smaller groups: the Gymnosperms and the Angiosperms. Basically, Gymnosperms have unprotected seeds while Angiosperms have their seeds develop inside a complex structure called the flower.

Gymnosperms had their hour of glory in the Jurassic period, around 150 million years ago. Today, they total around 700 species. They also include the so-called living fossil, the Ginkgo tree, as well as all the coniferous (resinous) trees such as the pines, fir, spruce, tamarack, hemlock, yew, cedar and cypress trees.

Angiosperms are the flowering plants. With around 230 000 species, they are the most numerous group of plants. They are also divided into two groups: Monocotyledons and Dicotyledons.

Monocotyledons, as their name indicates, have a single cotyledon (the first leaf of the germinating plant) sprouting from their seeds. Their leaves have parallel veins and their flowers part in multiples of three. Mostly herbaceous plants like grasses, lilies, orchids, they also include also the palm trees growing in warmer climates.

Dicotyledons, on the other hand, have two cotyledons coming out of their seeds. Their flowers develop either in multiples of four or five. Half of them are woody plants, including nearly all the deciduous trees, while many others are herbaceous such as mint, thistle, ragweed or strawberry plants, etc. .