Friday, 10 March 2017

The snowdrop (Galanthus nivalis)

Getting into botany requires learning a lot of new terminology and this can be daunting for the beginner.  It is best to learn by actually looking at examples of different flower families and that can be done using common species that can be found in the average garden.  All you need for this one is a hand lens and a sharp blade

The scientific name of the snowdrops (Galanthus) is derived from the Greek gala meaning milk and anthos meaning flower.  The species name (nivalis) is Latin for snow.

The flowering plants are divided into two large groups, the monocotyledons and the dicotyledons, referring to the number of first leaves that emerge from the seed when a plant germinates.  This isn’t a helpful distinction to identify flowers but there are a number of clues that can be seen in the snowdrop that indicate they are monocotyledons. 

  • the veins of the leaf are parallel to one another and the leaves are long and thin
  • the flower parts are in multiples of three

The snowdrop flower consists of six white sections that one might call petals - three of them longer and rounded at the tips and three shorter ones with a notch at the end outlined in green.  In this case the botanical term perianth segment is used because you can’t tell whether they are petals or sepals.  There are three longer outer perianth segments and three shorter inner perianth segments, forming two whorls.  The perianth segments are attached to the end of the ovary which is obvious and green.  This flower is described as having an inferior ovary (rather than superior or half-inferior).  Unfortunately botanists also use another term for the same thing, calling the flower epigynous (epi = on top of; gynous = female parts).  Both terms refer to the ovary being underneath the other parts of the flower. Inferior emphasises the position of the ovary below the other parts and epigynous emphasises that the other parts of the flower are on top of the ovary.  When in bud the flower is enclosed in a single leaf-like structure termed a spathe.

If the outer perianth segments are removed along with one of the inner perianth segments and one of the stamens, the other parts of the flower are visible. 

From the centre of the ovary there is a narrow green style with the tip hardly differing in structure, termed the stigma.  These three structures make up the female parts of the flower and are collectively called the gynoecium.

Around the style there are six stamens.  The stamens are made of a thin white filament which is attached to the base of an orange anther which tapers to a point.  The anthers contain the pollen which can be seen in the photograph, staining the inside of one of the perianth segments and the stigma.  The stamens (anthers + filaments) are the male parts of the flower and are collectively called the androecium.  The position on the anther where the filaments attach is important.  In this case they are attached to the base of the anther so they are termed basifixed.  How the anthers open is also important - the opening of the anthers to release the pollen is called dehiscence.  Here the anthers open by a slit which opens towards the centre of the flower and this condition is called introrse dehiscence

If you cut the ovary through lengthways using a blade the internal structure can be seen.  The outside wall encloses hollow sections which are called locules.  These are packed with white ovules which are attached to the central axis of the ovary.  If the ovary is cut across it can be seen there are three locules.  After the ovules are fertilised they become the seeds and the ovary becomes the fruit.  

The snowdrop is placed with other genera in family Amaryllidaceae which share the following features
  • perianth in two whorls of three rather similar segments, both coloured rather than green
  • flowers containing both male and female parts
  • ovary inferior / flower epigynous
  • six stamens
  • narrow leaves

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