XCII. — PENNY CRESS. 
Thlaspi arvense Linne. 
C LOSELY related to the Alyssine,^, the Tribe Thlaspide<e have white flowers ; 
short pods on horizontal stalks ; straight cotyledons ; and an accumbent 
radicle. Their pods are, however, compressed laterally, that is, at right angles to 
the septum, which is consequently very narrow (angustisepi) ; and open with two 
boat-shaped valves. 
The genus Thlaspi is further distinguished by having its petals equal and its 
pods roundish, winged, notched at the top, and containing more than four seeds. It 
comprises some sixty species, inhabiting Arctic, Alpine, and Temperate regions chiefly 
in the Northern Hemisphere, three or four of them being British. The scientific 
name Thlaspi^ strange-seeming to English, or even to Latin, ears, was adopted by 
Linnaeus from Dioscorides, and is, no doubt, derived from the Greek dXdo), thlao^ I 
flatten, referring to the fruits, which are far more conspicuous than the flowers. The 
modern English book-name Penny Cress has obviously the same origin, coming, 
perhaps, from the German Pfennigkraut^ while the French Tabouret^ literally “ a 
foot-stool,” refers to the same part of the plant. 
William Turner in his “ Names of Herbes ” (1548) says of it : — 
“Thlaspi or thlaspium is called in duche Baurensenfe. It groweth wonders plentuously about Bon in the come fieldes, and 
among the come. It groweth also plentuously besyde Syon. It may be named in englishe dysh Mustard, or triacle Mustard, 
or Boures Mustard, because the seede is lyke mustarde scede in colour and in tast, and the vessel that conteyneth the seede is 
lyke a disshe.’* 
Lyte translates the German name as Bower s Mustard ; while Gerard corrupts this 
into Bowyers Mustard^ while translating the original as Churl' s Mustard. The name 
Mithridate Mustard has been wrongly transferred to this plant from the somewhat 
dxvcvMx Lepidiurn carnpestreVtro'fin. This name and the connected Treacle-mustard recall 
a long romance in the history of medicine. Mithradates Eupator VI, king of Pontus 
from 1 20 to 64 B.C., whose name is also preserved in that of both the very different 
plants we know as Agrimony, was the hero of a remarkable story. Succeeding his 
father when a mere boy he was for seven years pursued by assassins. With an 
intellect in advance of that of most of those about him, he acquired the reputation of 
a magician, and was believed to have so saturated his body with poisons that no 
poison could have effect upon him. Thus when, defeated by Pompey, he wanted to 
poison himself, he could not, and ordered one of his soldiers to stab him. In 
primitive civilisations the venom of serpents, or other wild animals known, or 
supposed, to be poisonous, is a main ingredient in the noxious mixtures used to 
anoint the dagger of the assassin or as fatal potions to be administered to the enemy. 
Thus a remedy against venom and poison became a OrjpiaKrj, theriake, from drjpLov, 
therion, a wild beast, and such theriacs, triacles, or treacles came to be known also as 
Mithndates. 
