| Sori of Tectaria vasta |
| A
general morphological explanation Each of these circular brown 'spots' that you see in the photo below is called a sorus (plural - sori). A sorus is a tight group of spore cases (called sporangia; singular - sporangium) arising from a minute stalk which cannot be seen with the naked eye. |
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| In
the case of T. vasta, each stalk is topped by an umbrella-shaped scale.
A scale is a term for a flattened or membranous hair. The umbrella-shaped
scale spreads out and protects the underlying immature sporangia.
This protective scale is called an indusium, and the sori that possess
them are therefore termed 'indusiate sori'. See indusia
of Tectaria vasta. However, the indusia that can be found in different species of ferns are not always umbrella-shaped. They may be kidney-shaped, round, vase-like and pocket-like, etc. And not all ferns produce sorus with indusium too. Such a sorus is described as 'naked' or exindusiate, i.e. without indusium. In describing a sorus, take note of the presence and character of the indusium (which is usually best seen in immature sorus). It is also very important to record the arrangement and position of the sori in relation to the veins, leaf margin or midrib. In some ferns, the sori develop so closely together that they form an unbroken line. That would be considered a good diagnostic character useful for identification and classification. You won't be able to see the indusia in the photo below as they have shriveled up. The indusia have 'given way' just when the sporangia were ripening and splitting (photo above). This has allowed the spores to be ejeculated from the sporangia far afield. Such is the beauty of nature! Like the indusia, we parents have to take that crucial step to 'let go' of our children and allow them to lead their own lives as they see fit at some point in their growing up. We can only wish them a blessed journey ahead. |