地衣類 lichen

　苔のように見える、墓石に張り付いたものは、地衣類です。日本には、約1,800種の地衣類が生育しています。菌類が藻類を体内に住まわせている共生体で、菌類が藻類に生息場所や水分を与え、藻類は菌類に光合成で作った栄養を分け与えます。共生にもいろいろありますが、お互いに利益を与えあう相利共生です。アリとアブラムシ、ヤドカリとイソギンチャク等の関係も同じです。
　この墓石のあるお寺には、浄行菩薩縁起が掲げられており、それには、体の悪い部分を念入りに洗えば、菩薩さまが身代わりになると書かれています。寺務所には、体を洗う「たわし」が用意されています。
　地衣類は、南極圏や北極圏、そしてヒマラヤやアンデス山地などの厳しい環境下でも生育していますが、「たわしがけ」には弱いと思います。

　What looks like moss clinging to the gravestone is lichen. There are approximately 1,800 species of lichen growing in Japan. This is a symbiotic relationship in which a fungus hosts algae within its body; the fungus provides the algae with a place to live and water, and the algae shares with the fungus the nutrients it produces through photosynthesis. There are several forms of symbiosis, though this particular one is called mutualism, where both parties gain from each other. The relationships between ants and aphids, hermit crabs and sea anemones, and so on are also examples of mutualism.
　At the temple where this gravestone stands, there is a plaque detailing the legend of Bodhisattva Pure Practices, which states that if you thoroughly wash the ailing part of your body, the Bodhisattva will take your place. The temple office provides "scrub brushes" for washing your body.
　Lichen grows even in harsh environments such as the Antarctic and Arctic regions, as well as the Himalayas and the Andes, but I think it is vulnerable to being scrubbed with the scrub brush.