Tuesday 31 July 2012: Anyone for cecidology?
If you don't know what cecidology is, now's your chance to learn.
It's the study of plant galls. Galls are abnormal growths on plants stimulated by another organism, such as a fungus, or an insect. The host cells enlarge or proliferate in such a way as to provide shelter or nourishment for the invader to reproduce itself. Any part of a plant can be involved - leaves, stems, fruit - but the resulting galls are always characteristic of the particular pathogen. Familiar examples are the witches' broom twig clusters on birch trees (often assumed to be birds' nests) and the bedeguar or robin's pin cushion galls on wild rose briars and marble galls on oak trees. There are many others, certain trees and plants being especially susceptible. Although they can look grotesque they usually do little harm to the host.
Galls are one of the many natural phenomena that I find fascinating. I'm always thrilled to find one that's new to me and yesterday I spotted these female alder cones (more correctly, catkins) sprouting curious pink tongues. Some were single outgrowths like this, others had produced whole explosions of curlicues like finger-nails left to grow rampant.
Turns out this is the not-very-imaginatively-named Alder Tongue Gall produced by the fungal pathogen Taphrina alni. The growths are known as languets (tongue-like things!) so I've collected a new word as well as a new gall.
In the picture you see young green alder cones which are around 2 cm. in length. The production of the red 'tongues' has been triggered by the fungal infection - they are composed of plant material, essentially for the purpose of providing the fungus with material from which to disperse its spores - they are not themselves the fungus, which is microscopic.
As the year wears on the tongues will mature along with the cones and can be seen in winters still in situ but dry and blackened.
Another of nature's miracles, but perhaps a rather disturbing one.
Was Einstein infected by this gall fungus? (See here for discussion of tongue extrusion.)
The British Plant Gall Society