Well, it’s been pouring. The English Summer app is running, sort of, only the running is as in “running water”. The pavements in my street are wet enough to support flourishing colonies of the greenhouse liverwort Marchantia polymorpha. It is named polymorpha as it has many (poly-) forms (morph-). Two of these are rather splendidly visible in the photo.

Firstly, the female plants have decorative little umbrellas with star-shaped tops, which are gametophores which carry the female gametes, the ova.The flat green thallus is lobed like a liver, which by the mediaeval doctrine of signatures was supposed to be God’s way of indicating to the herbalist that this was a useful medicine for the liver … no worse than the modern crackpot ideas that Ben Goldacre ridicules in Bad Science, I guess.

Secondly, sticking up from the top of the thallus (try the top right of the photo) are little circular cups containing gemmae, small discus-shaped blobs of tissue. When a raindrop (yeah) splashes into the gemma cup, the gemmae ricochet out and land a little distance away, ready to grow, asexually, into new liverworts.They do this so well that stream banks are often carpeted with the little plants; and so are greenhouse pots.

Male plants (not shown here) have circular gametophores instead of the female star-shaped ones. Quite a lot of fun and curiosity from a small corner of pavement, really. In a sufficiently wet year, of course.