In 2004 I encountered some strange growths on the glasswort (Sarcocornia quinqueflora), a common saltmarsh plant of the Amaranth family (Amaranthaceae) in Southern Australia and Tasmania.
Knowing little of the glasswort, I thought the structures were it’s succulent fruits. It was a few years later after I had encountered the phenomenon a couple more times that it started to occur to me that those structures might be galls. Winifred Curtis in the Student’s Flora described the phenomena as follows:
‘…short lateral branches or small groups of segments…enlarged and bright red in colour, superficially resembling flowers.‘
This was hard to believe as my impression of galls were deformed lumps on leaves or twigs that disfigured the overall appearance of a plant. The galls on the glasswort on the other hand had a symmetrically beautiful form, with tightly overlapping succulent scales forming a pegoda-like structure.
A quick search online brought me to the profile page of Dr Anneke Veenstra from the Deakin University. In 2007, she and co-workers published a paper on the minute gall midges that were the cause of the flower-like galls on the glassworts. They described the gall midge as Asphondylia floriformis, classed under the Cecidomyiidae, a family under the large order of Flies (Diptera). The specific epithet ‘floriformis’ alludes to the flower-shaped appearance of the galls.
How the galls are formed has yet to be studied in detail but presumably this happens in spring when the adult gall midge deposits an egg via it’s ovipositor into the plant tissue. A local swelling then arises. The larvae of the gall midge then develops in a chamber of the gall. The chamber walls are also observed to develop a covering of fungal mycelia (threads), which I suspect might play some role in the development of the gall midge larvae. When mature, the gall midge makes it’s way out of the top of the gall and leaves behind the cocoon covering.
Interestingly, glasswort plant collections with galls date back to the mid 19th century. The first known collection of the glasswort with galls on them was made in 1859 by German-born doctor and botanist Hermann Beckler in Hastings River, New South Wales. Since then, there have been numerous glasswort collections with galls from various Australian states, including Tasmania.
From the notes accompanying the collections, it is evident that some of the early collectors did not recognize the galls and thought they were floral parts. Another thought the galls to be vegetative plantlets that would eventually fall off to establish new plants. I imagine that some of these early collectors did not think that the swellings were galls because it’s ‘natural’ and aesthetic look.
In it’s normal, healthy state, the glasswort is by no means a highly adorned plant. The inconspicuous flowers are borne on fleshy spikes that look just a little more compact than the normal segments that make up the glasswort’s succulent body. Functionality and simplicity is it’s style. But when dealing with an attack from a natural parasite, the glasswort reveals it’s somewhat macabre capacity for morphological aesthetics. Few other plants can claim to have the gall to be beautiful.