Poikilohydry

I've been taking lots of pictures of moss lately because I'm reading a lovely book called Gathering Moss, A Natural and Cultural History of Mosses by Robin Wall Kimmerer. (She   also wrote Braiding  Sweetgrass mentioned here by Kendall.)

It's been raining a lot in Wales and mosses love rain. They need to be wet in order to breath and to breed. Unlike vascular plants they take carbon dioxide from  water, not air, so they need their surfaces to be wet. That's why they grow close together in thick tangled mats or cushions that retain water like a sponge. They also need it to reproduce because the sperm swim to the eggs via the surface moisture.

But, while being so dependent on wetness, they can also tolerate drought - unlike leafy plants that wither and die. Mosses can stand desiccation for long periods (which is what poikilohydry means) and can  revive  when in contact with water again even after years in laboratory specimen box.

"Only twenty minutes after wetting, the moss can go from dehydration to full vigor". 

Kimmerer writes beautifully and joyfully about such miracles and extends her passion  to show how,  by "looking through moss-coloured glasses",  it's possible to see how meshed and intervoven are all forms of life, each interdependent with others, in the human as in the natural world.