Back to the home page  

        Identify a Euphrasia

small bee

You do not need to answer every question, though the identification will be more reliable if you do.

You can download a PDF crib sheet for the questionnaire here.

Also bear in mind the following points.

  • The best time to identify Euphrasia is in the summer when there are both capsules and flowers on the plant.
  • It is important to read through the full list of choices before choosing one.
  • Read the notes associated with the question.
  • For the most reliable results, use fresh material from healthy plants.
  • Determine the answer to the questions after looking at several average plants in the population.
  • Do not uproot plants, but try and determine the answers to the questions in the field.

 
How long are the cauline leaves (mm)?
The leaves of Euphrasia can be divided into two types. The upper ones with a flower or capsule in the axils of the leaves and lower ones not associated with flowers. The cauline leaves are the lower ones without flowers. Measure the length (mm) of the larger leaves from their base to their tip. How to measure leaf length
Are the lower floral leaves alternate?
  • I do not know
  • Yes
  • No
In general the leaves of Euphrasia are held on the stem in opposite pairs (A). However, the lower floral leaves can be alternate (B). If they are, answer yes to this question. (A) opposite leaves. (B) alternate leaves.
Are the leaves hairless?
  • I do not know
  • Yes
  • No
To see the hairs on a Euphrasia leaf requires a hand lens. Look on both sides of the leaf for hairs, before deciding on your answer.
Do the leaves have glandular hairs?
  • I do not know
  • Yes
  • No
Glandular hairs may be seen with a hand lens. They resemble miniature lollipops. There is a translucent globe-shaped head attached to a narrow stalk. Although this character is quite tricky for beginners to assess, it is worth persisting with, as it is particularly helpful in distinguishing species. A glandular hair
How many pairs of teeth are there on the lowest floral leaves?
The lowest floral leaf is the lowest leaf on the main stem with a flower or capsule associated with it. The teeth are in pairs, one at either edge of the leaf. leaf teeth
What colour are the flowers?
  • I do not know
  • Lilac
  • Purple
  • Reddish
  • White
  • Yellowish
Most Euphrasia have white or lilac flowers so this characteristic is only of limited help in distinguishing the species. Nevertheless, as flower colour is easily and reliably determined it is worth using it in the key. flower colour
What is the length of the corolla (mm)?
The corolla can be gently pulled from the calyx and measured across the top. How to measure corolla length
How pointed are the teeth of the lower floral leaves?
  • I do not know
  • Blunt (obtuse A)
  • Intermediate
  • Pointed (acute or acuminate B)
The lower floral leaves are the lowest leaves on the main stem that have a flower in their axil. Later on in the season the flower will develop in to a pod. The teeth of these leaves vary from quite blunt to narrowing to a long, fine point. This character exhibits a considerable amount of variability within a species. However, a few species are sufficiently uniform in this feature for it to help in their identification. Leaf Teeth
Which direction do the lowest teeth of the lower floral leaves point?
  • I do not know
  • Pointing away from the leaf tip (retrorse A)
  • Pointing outwards (patent)
  • Pointing towards the leaf tip (antrorse B)
The teeth closest the stem of the lowest floral leaves can either point out sideways; can be inclined in the direction of the leaf tip or they may point away from the leaf tip. The correct botanical terms are patent when they point outwards; retrorse, when they point backward and antrorse when they point forwards. Leaf Teeth
How long are the teeth of the lower floral leaves compared to their width?
  • I do not know
  • Broader than long (A)
  • As long as broad
  • Longer than broad (B)
Unless this characteristic is obvious, it can be quite tricky to determine without a microscope. Nevertheless, it is a valuable characteristic for identification and worth persisting with. Leaf Teeth
How pointed is the terminal lobe of the lower floral leaves?
  • I do not know
  • Pointed (acute or acuminate A)
  • Intermediate (sub-acute)
  • Blunt (obtuse B)
This characteristic is rather variable both between species and within species. Its value for identification is therefore limited. Still, it is easy to determine by eye or with a hand lens, which will be appreciated by many users. Leaf Tip
What month is the plant flowering in?

The primary months for flowering are July and August though some species can flower as early as May and as late as September. As there is only limited variability in the flowering times of Euphrasia this character will only of be of use in occasional circumstances. monthes
What is the ratio of the cauline internode to leaf length?
Cauline internodes are the lower internodes on the stem without flowers in the axils of the leaves. Divide the length of these internodes by the leaf length. A simple estimate of this parameter can be made by bending the leaf up against the stem. If the leaf is the same length as the internode then the ratio of internode to leaf length is 1. If the leaf is half the length of the internode then the ratio of internode to leaf length is 2. internode length.
What is the ratio of the lowest floral internode to leaf length?
Divide the length of the lowest floral internode by the length of the leaf at the lowest floral internode.
What is the length of the capsule (mm)?
Measure the length of the mature capsules in millimetres. capsule length.
What shape is the end of the capsule?
  • I do not know
  • Retuse (A)
  • Emarginate (B)
  • Truncate (C)
  • Rounded (D)
The end of the capsule may be blunt, rounded or indented. However, determining the precise shape can be tricky. Particularly, when trying to differentiate either between retuse (A) and emarginate (B) capsules or truncate (C) and rounded (D) capsules. If you are unsure it is better to try different options to see what difference it makes. capsule end shape.
How wide is the capsule relative to its length?
  • I do not know
  • Capsule more than twice as long as wide (A)
  • Capsule about twice as long as wide
  • Capsule not more than twice as long as wide (B)
This can be a tricky characteristic to assess particularly in borderline cases. A hand lens may help. Imagine the pod cut in half. If that half is longer than the capsule is wide then choose “Capsule more than twice as long as wide” from the choices. capsule shape.
Is the calyx longer or shorter than the capsule?
  • I do not know
  • Capsule longer than calyx
  • Capsule equal to calyx
  • Capsule shorter than calyx
The calyx sheathes the capsule and ends in a toothed rim. This question relates to whether the capsule is longer than the calyx or whether it is shorter. calyx length.
Is the capsule hairy?
  • I do not know
  • Yes
  • No
Look at the end on the capsule with a hand lens. If the are long white hairs on the capsule answer "Yes" else if there are either no hairs or a few short ones answer "No". capsule hair
How many nodes to the lowest flower?
Count the number of nodes up the stem to the lowest flower or capsule. Do not include the cotyledonary node. Once some leaves have fallen, count the leaf scars they leave behind on the stem. It may be hard to see these scars, in which case, use a hand lens to find them. number of nodes to the lowest flower.
How many pairs of branches does the plant have?
The branches of a Euphrasia grow in pairs. Count the number of these branch pairs along the main central stem. Ignore those plants where rabbits or sheep have eaten the main shoot, as this forces the plant to branch more than usual.
What colour is the stem?
  • I do not know
  • Purple
  • Green
The stem is usually either green or purplish in colour. stem colour
Are the branches branched?
  • I do not know
  • Yes
  • No
The side branches of Euphrasia may be branched again. If they are select Yes. If there are no side branches or if there are no branches at all then choose No. Determination of this character can only be made on plants that have not been nibbled by sheep or rabbits. branches branched.