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A closer look inside

The fieldwork of the B1 project is long over and all samples were collected. The determination process is still running and we want to take you along that process.For the identification of species different morphological structures are important. For lichens different growth forms, like leave-like, beard-shaped or crustose, were distinguished and also the colour of the lichens thallus is important. Furthermore, the determination keys distinguish between the production of different sexual propagules, called apothecia or perithecia, or asexual propagules, called soredia or isidia. These morphological structures are visible on the outer surface of the lichen thallus. For bryophytes also, morphological structures, like the growth form, are important. The first step is the discrimination between mosses, hornworts and liverworts. These different groups have than different characteristics to distinguish the species of the single groups.
When we look into the mosses for example, they will be firstly distinguished on the position of the sporophytes for determination. Acrocarpous mosses have their sporophytes on main branches and the stems are not with lot of branches; the pleurocarpous mosses are highly branched and the sporophytes are built on side branches.

But for the identification process of lichens and bryophytes it is in most cases not sufficient to use only morphological structures which are visible on the outer surface of the organisms. Often it becomes necessary to identify inner structures of lichens and bryophytes. During the identification of mosses, the shape of the leaves and the structure of the leave cells, for example, are important. For that microscopic investigation of the single leaves need to be done.
For the identification of lichens, the photosynthetic partner and the shape of the spores become important. To investigate both, thin cross sections of a lichen thallus are necessary, they can be done with a razor blade. Such cross sections enable us to see into the organism. It is like cutting a cake into pieces, to see which cream is inside. For the investigation of spores, the sexual propagules (apothecia or perithecia) will be cut in the same way. The different shapes, sizes and colours can then be seen and used for discrimination of the species.

These mentioned structures are an example of what important structures are hidden inside, which become important in the identification process. It would become too messy to designate all of them here. It is more the purpose to show the diversity of different shapes and structures nature produces and to show the complexity of species determination. Also, to give a little inside in the amount of work projects with species identification harbour. Nevertheless, the huge amount of work is worth it and can be much fun, when you enjoying microscopy. :)

by Dina Emrich (B1)