Freitag, 28. Februar 2014

Plant of the Day (February 28th, 2014) - Bryum argenteum Hedw.

Today's “Plant of the Day” is Bryum argenteum Hedw. from the Bryaceae family. In English, the species is known as “Silver moss”. The German name is “Silbermoos” but “Silber-Birnmoos” is also very common.

1) Description

B. argenteum grows in dense and compact turfs. The cylindrical shoots of the Gametophyte are mostly around 1 centimeter long, so it isn't a very tall moss. However, these shoots are densely covered with small “leaves” (we call them leaves but in fact, mosses have no real leaves like the higher plants). These leaves are tiny and only between 0.5 and 1.25 millimeters long.

B. argenteum -between to concrete plates

However, the leaves are a distinctive character of identification for this species. There are two kinds of them: the basal leaves of the shoot and the leaves, which are located at the top of each shoot. The basal leaves are more spade-shaped, while the other leaves are more round but with a significantly narrowed tip. This tip has no chlorophyll and as a result a silver to white color, when dry. 

B. argenteum - habitus; you can see the silver tips
In both cases, the leaves are concave curved and have a leaf rib on their dorsal site. However, these rib goes not to the tip but ends in the middle of the leave blade. Both kind of leaves lie directly on the shoot like scales. However, protruding leaves are also possible; especially in the dry state.

 B. argenteum - the distinctive, silver shimmer

By the white color of the leaf tip, which I've described above, the stocks of B. argenteum shimmer silver, when dry. This is also the reason for the name of the species (“Argentum” is Latin and means “silver”).

The Sporphyte of B. argenteum is kept simple with a Seta and a capsule, which contains the spores. The Seta is about 1 centimeter long. The capsules at the end are pendulous or nearly horizontally. They are produced between autumn and spring.

2) Distribution

B. argenteum is a cosmopolitan and widely distributed. It benefits largely by the anthropogenic influence, because it prefers nutrient rich places to grow. Thereby, the species can be found nearly everywhere like ruderal wastelands, railway line or even in the cracks between concrete slabs. 

B. argenteum - is widey distributed in urban areas
As with the most species, B. argenteum can grow even under the most adverse circumstances and has also the ability to endure longer periods of dryness.

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