The plant shown in the logo background is Tribulus terrestris L. (Zygophyllaceae),
a quite well known, pubescent, procumbent annual, 10-60 cm
tall, typically growing in dry open
habitats (including dry deserts).
A cosmopolitan
plant, initially a native of Middle East and the Mediterranean rim, Tribulus
terrestris is currently naturalised on all continents, in areas with warm
temperate conditions (a summer annual). Its large geographical distribution is
most probably due to epizoochory.
The fruit is composed of 5 stellately arranged, hard schizocarps, each of
which bears 2 or more (usually 4) stout spines on the sides. The spines of
the‘woody burr’ are so sharp and rigid that are
strong enough to puncture bicycle tires, penetrate shoe soles and injure feet of humans and stock. Usually considered a noxious weed, Tribulus
terrestris (puncturevine, caltrop) can grow on almost any type of soil and
is found in pastures, roadsides, orchards, vineyards, waste places, parks,
railway yards and agricultural areas.
The word Tribulus comes from the ancient Greek ÔÑÉÂÏËÏÓ (trivolos), meaning 3-pointed and probably referring to the spined-schizocarp (which is usually
4-spined!). Its vernacular name in modern Greek is still ‘trivoli’. The specific
name terrestris is obviously due to the fact that the name ‘trivolos’
was applied to 2 different kinds of plants (as described by Theophrastus), the
latter one being the aquatic species Trapa natans (Theophrastus HP
4.9.1.-3.). Moreover, Dioscorides, when describing the kinds of ‘trivolos’
names the former ‘terrestrial’.
The
plant is given considerable attention by Theophrastus. Its exceptional characteristic of
bearing spines on the pericarp is mentioned twice (HP 6.1.3., 6.5.3.);
further descriptions refer to the prostrate habit, the chick-pea-looking leaves
and the sesame-like seeds (HP 6.5.3.). Finally, a striking citation
concerns soil seed
banks: ‘trivolos’ is reported to emerge when a partly saturated soil
is stirred. (HP 3.1.6.: ‘And in some places, if the ground is merely
lightly worked and stirred, the plants native to the district immediately
spring up; for instance the cypress in Crete. And something similar to this
occurs even in smaller plants; as soon as the earth is stirred, wherever it may
be, a sort of vegetation comes up. And in partly saturated soil, if you break
up the ground, they say that ‘trivolos’ appears.’)
The
plant is illustrated quite precisely (*) by an
unknown Byzantine artist in the first-ever
collection of botanical drawings (512 AD), which
complemented the treatise of Dioscorides
De Materia Medica (1st c. AD). (*) Fruits are
consistently illustrated (there are 8 fruits in the drawing) as 6-merous while
they are indeed 5-merous (see also the font of this page).
‘Trivolos’
is also found in Ancient Greek
texts preceding Theophrastus (eg Alcaeus’ poems, 6th c. BC; Aristophanes’ Lysistrata,
412 BC) as well as in the Bible
(Genesis 3.17, 3.18; Hosea 10.8; Matthew’s Gospel 7.16-17 – ‘are grapes
gathered from thorns or figs from trivolos?’; Paul’s Epistle to the Hebrews
6.8).
Each
schizocarp (dispersal unit) contains several, non-endospermic seeds which are known to be dormant
(germination is manifested at relatively high temperatures and some, at least,
afterripening is required; Ernst
W.H.O., Tolsma D.J. 1988. Dormancy and germination of semi-arid annual
plant species Tragus berteronianus and Tribulus terrestris. Flora
181, 243-251). Seeds germinate in late spring and
early summer under suitably moist conditions but further research is
needed for full elucidation of its germination ecophysiology.
