Thyrse - What is it and Why is it in the Bromeliad Glossary

By: Derek Butcher

Tillandsia thyrsigera is a Mexican plant not that common in collections, but it has a striking inflorescence and was the. start of this investigation. There are other "thyrsoid" inflorescences including T. parryi, T. sueae and others. Renate Ehlers, Pamela Koide and others have been collecting roughly in the same area in Mexico and have had exciting finds. No doubt we will see new species being named. The name "thyrse" had me intrigued because as far as I was aware it was a botanical description of how the flowers were arranged in the inflorescence.

So I looked up Benzing's Biology of Bromeliads where it states that all Bromeliad inflorescences can be described as a panicle or a condensation of a panicle. No reference to a thyrse and I couldn't understand the definition in the Bromeliad Glossary of the B.S.I. I quote... "Thyrse - a compact, more or less compound, panicle; more correctly a panicle-like cluster with the main axis indeterminate. Can be ovoid-pyramidal or cylindrical". To me this sounds gobbledegook and not particularly informative.

To clear things up in my own mind I paid a visit to a Botanist acquaintance at the Adelaide Botanic Gardens. I couldn't understand the explanation over the telephone!
Gradually it dawned that there was a THYRSE in the general sense and a THYRSE in the strict sense! How do you know if someone is writing in the general sense or the strict sense? Apparently in recent years botanists including Weberling, Troll and others have been redefining the arrangements of inflorescences but it was all too technical for me. What relevance did it have to Bromeliads? If you are interested, just have a look at the convolutions in the inflorescence of Syringa vulgaris, commonly called 'Lilac'. This is said to be an example of a thyrse.

So I decided to write to me mate, Harry Luther. As is usual with Harry I got a short reply, "No Bromeliad has a thyrse"..

If only for my own peace of mind we should try to influence those who write descriptions of new species not to use the term "thyrse" or even "thyrsoid" when clearly they are describing the shape rather than the arrangement of a compound inflorescence.

There are 4 or maybe 5 main shapes and we must remember they are 3 dimensional. This I can understand, and perhaps examples will show what I mean.

(1) CYLINDRIC e.g. T. bourgaei or T.cossonii
(2) OVOID (like an egg)
ELLIPSOID (like a flattened egg):
e.g. T.cerrateana, or T.heteromorpha
e.g. T. mauryana, or T. sphaerocephala
or T. heteromorpha or T. capitata
(4) CONICAL e.g. T.guatemalensis, T. leiboldiana, T.secunda.
(5) RHOMBOID e.g. Some forms of T.fasciculata.

Rarely will a compound inflorescence correspond exactly with these shapes but they do give a guide. You will also read of combinations of these such as ovoid-cylindric and the use of the word "sub" which means "almost" to make things even more vague. Oh, by the way, "conical" is the upside-down version when the icecream falls out!

So when the Tillandsias with ovoid-conical shaped compound inflorescences become more common, as they are sure to do, and someone describes them as having a thyrse or are thyrsoid please ask them to explain it to you.

When is a thyrse not a thyrse? Can anyone tell me why it is in the Glossary?