Identifying Fungi by Microscopy.
Although many fungi can be confidently identified ‘in the field’, there are a large number of species which can only be correctly identified by analysing them under the microscope.
In order to identify many of the tiny fungi illustrated here and many more which look very similar, it is necessary to collect some of the fruit bodies as a sample to take home. A brief written description of the fungus, including a note of the host substrate can also be useful, as many species will change colour and/or shrink as they dry out.
A microscope slide should be prepared either by cutting and squashing a tiny fruit body or a small section of the fertile part and any marginal hairs of a larger fungus. A drop of water, or a dye designed to enable the cell walls to be seen, should be added before a cover slip seals the sample in readiness for microscopy.
Under the microscope, it should now be possible to see any of the important characteristics which will be used for identification. These include the spores, acsi (sacs containing the spores), paraphyses (infertile structures between the asci), hairs, and the structure of the exterior of the fungus.
Reference books should be consulted to complete the identification. Some books have colour photographs illustrating the fruit bodies, whilst others rely on black and white line drawings. The books may also recommend the use of a chemical such as iodine to test for a colour change reaction. If so, a second slide should be prepared using the chemical instead of the water or dye previously used.
As an example, I offer the following for the tiny pink and white cups illustrated on this page.
In the field a note such as "Tiny pink and white cups with stalks growing in large numbers on a dead stem of buckler fern.
Collect a piece of the dead stem with at least 6 of the larger fruit bodies.
Back home, remove one of the larger fruit bodies with a scalpel, and place on a microscope slide.
Cut a slither from the edge of the cup and squash the remainder onto the slide, keeping it all in a small area.
Place a drop of water or dye onto the cut and squashed material and cover it with a cover slip, removing any excess liquid from around the cover slip.
Use the smallest microscope objective to find and focus on the squashed material. Move up through the objectives to the x40, refocusing for each.
Locate the asci containing the spores to see the shape and size of the spores inside them and then find some loose spores. A drawing of a spore is useful and measurements, using the graticule inside the eyepiece, of the length and width of the spores should be noted. In this case, measurements between 10 and 15 x 2.5 – 3 microns.
Also note the colour of the spores (colourless in this case), the presence or absence of circular oil drops (2 large drops in this case), the number of cells in the spores (1 in this case), whether the spores are smooth or roughened by granules, warts, spines etc. (smooth in this case).
If there are hairs on the cut slither of the edge of the cup or elsewhere, draw and measure these, noting their colour. (No hairs in this case).
This fungus can now be identified as Allophylaria campanuliformis, which may be found growing on various species of fern. (Lit. = Microfungi on Land Plants by Ellis & Ellis, p562, fig. 2083).
Although many fungi can be confidently identified ‘in the field’, there are a large number of species which can only be correctly identified by analysing them under the microscope.
In order to identify many of the tiny fungi illustrated here and many more which look very similar, it is necessary to collect some of the fruit bodies as a sample to take home. A brief written description of the fungus, including a note of the host substrate can also be useful, as many species will change colour and/or shrink as they dry out.
A microscope slide should be prepared either by cutting and squashing a tiny fruit body or a small section of the fertile part and any marginal hairs of a larger fungus. A drop of water, or a dye designed to enable the cell walls to be seen, should be added before a cover slip seals the sample in readiness for microscopy.
Under the microscope, it should now be possible to see any of the important characteristics which will be used for identification. These include the spores, acsi (sacs containing the spores), paraphyses (infertile structures between the asci), hairs, and the structure of the exterior of the fungus.
Reference books should be consulted to complete the identification. Some books have colour photographs illustrating the fruit bodies, whilst others rely on black and white line drawings. The books may also recommend the use of a chemical such as iodine to test for a colour change reaction. If so, a second slide should be prepared using the chemical instead of the water or dye previously used.
As an example, I offer the following for the tiny pink and white cups illustrated on this page.
In the field a note such as "Tiny pink and white cups with stalks growing in large numbers on a dead stem of buckler fern.
Collect a piece of the dead stem with at least 6 of the larger fruit bodies.
Back home, remove one of the larger fruit bodies with a scalpel, and place on a microscope slide.
Cut a slither from the edge of the cup and squash the remainder onto the slide, keeping it all in a small area.
Place a drop of water or dye onto the cut and squashed material and cover it with a cover slip, removing any excess liquid from around the cover slip.
Use the smallest microscope objective to find and focus on the squashed material. Move up through the objectives to the x40, refocusing for each.
Locate the asci containing the spores to see the shape and size of the spores inside them and then find some loose spores. A drawing of a spore is useful and measurements, using the graticule inside the eyepiece, of the length and width of the spores should be noted. In this case, measurements between 10 and 15 x 2.5 – 3 microns.
Also note the colour of the spores (colourless in this case), the presence or absence of circular oil drops (2 large drops in this case), the number of cells in the spores (1 in this case), whether the spores are smooth or roughened by granules, warts, spines etc. (smooth in this case).
If there are hairs on the cut slither of the edge of the cup or elsewhere, draw and measure these, noting their colour. (No hairs in this case).
This fungus can now be identified as Allophylaria campanuliformis, which may be found growing on various species of fern. (Lit. = Microfungi on Land Plants by Ellis & Ellis, p562, fig. 2083).