This section of RG was inspired by a posting from one of our members - Dee.   She has kindly shared her knowledge with us so that we will understand more about Botany as opposed to Horticulture.  

First of all an explanation of what Botany is.  Horticulture is the "how", botany is the "why"

For instance:   A gardener (horticulturalist) will know how to grow a great lawn, a botanist will know why grass cuts your fingers.

A gardener will know how to grow a lovely white flower such as Tracleospermum jasminiodes, a botanist will know why the scent gets stronger at night.

A gardener will know we have very few native wildflowers that are red, a botanist will know why the majority of red flowers are from hot countries.

For an example lets take the orchid  -  Orchidaceae habaneria radiata. 

Orchidaceae is the Family  (every single orchid is a member of the Orchidaceae).

Habenaria is the Genus.   It is a higher level category than species and includes all members of that species.

Radiata is the  Species.   This is a smaller division, and is usually an epithet (descriptive word) mainly from Greek or Latin, that helps describe a characteristic, as in this case rayed or radiating.

Egret Flower is the  Common Name.   Common names are misleading, as several flowers can be known by the same name in different countries.  The scientific name will get you the same plant in The USA, China or the UK, or indeed anywhere in the world that sells it.

Sometimes you may see something like Habenaria radiata  ‘Blanche’ . This means that the plant has either been specially bred or selected.   It may have larger flowers or a better growth habit, one or a combination of attributes that may be an improvement on the species, and is known a  Cultivar or Variety.

THE KINGDOMS

Although this course is predominately about plants, first we look into where plants fit into the life on earth.

This is the broadest division of organisms.   Top level of classification.  Originally there were just two kingdoms Animalia and Plantae – basically Animals and Plants.

Many unicellular (single-celled) and simple multi-cellular organisms did not fit comfortably into either category, so in 1866 the zoologist Ernst Heinrich Haeckel proposed a third kingdom Protista, to include protozoa, algae, fungi and bacteria.  Two more kingdoms have been added up to the present day – Monera and Mycetae. 

Each of the Kingdoms are listed below in the order in which they are believed to have evolved, as well as a brief explanation of where Viruses stand in the order of things.

Monera

Primarily bacteria – these are considered some of the most primitive and earliest forms of life.  They are identified by having the DNA spread throughout the cell, rather than organised into a nucleus.  These are otherwise known as prokaryote cells.

Main divisions of Monera are Eubacteria, Archbacteria and Cyanobacteria, the latter probably better known as blue-green algae.

Protista

This for a long time has been known as the ‘junk kingdom’ a lot of organisms that do not comfortably fit into the other kingdoms have been dumped into Protista.  It includes Algae, diatoms and water moulds and slime moulds.  Everything in this kingdom has eukaryote (cells with the DNA organised into a nucleus).  The vast majority are very small and can only be seen with a microscope, and very many of them live in water or wet conditions.

Main divisions of Protista are Protozoa, Ameoboa, Dinoflagilates, Green Algae, Red Algae and Brown Algae.  Seaweeds are in this kingdom as they are algae

Animalia  

A fairly obvious kingdom, contain all animal life from the blue whale, through tigers to insects and worms.  The main divisions of Animalia are Vertebrates (anything with a backbone) and Invertebrates (anything without a backbone).

Plantae

This kingdom covers plants, but it may surprise you to learn that it is difficult to define precisely what a plant is. Plants have so many types and variations that a simple definition has too many exceptions, and a definition that includes all plants and excludes all non-plants may be too complicated to be useful.  Also biologists do not agree whether certain organisms are plants.

Your concept of plants is probably quite accurate. Most plants have green leaves, stems roots and flowers, but you can think of exceptions immediately.  Conifers, such as pine and spruce have cones instead of flowers, but are recognisable as plants as they so closely resemble organisms that are obviously plants.  Ferns and mosses are easily recognised as plants.  Fungi, such as mushrooms, were included in the plant kingdom until fairly recently, because they are immobile and produce spores, which function somewhat like seeds, but they are no longer considered to be plants as they differ from plants in many basic biochemical respects.

Algae are the most problematic. The green algae are similar to plants in biochemistry and cell structure, but they have many significant differences.  Some botanists conclude that it is more useful to include green algae with plants, others exclude them, pointing out that some green algae have more in common with the seaweeds known as red and brown algae.

The main divisions of Plantae are Angiosperms –(all flowering plants, including grasses) and Gymnosperms (which includes conifers, ginko, cycads, ferns and mosses).

Mycetae

This kingdom of the  fungi. They are a very important life form and one of the main agents in the decomposition of dead matter. The vast majority of vascular plants, especially conifers and all orchids are associated with a mutualistic fungus  (mutualism – better known as a symbiotic relationship), which assists the absorption of nutrients and water.

Viruses

Blue Green Algae

Fungi