THE MARSH PENNYWORT— continued. 
the seed is flat or grooved along the side facing the commissure. In the mericarp of 
Carum Carui Linne, commonly miscalled a Caraway-seed, whereas it is in fact half a 
fruit, the primary ridges are easily perceptible to the touch and distinguishable by the 
naked eye ; but in this very natural Family the genera can for the most part only be 
accurately discriminated by an examination of the number and relative development 
of the ridges and vittae and the form of the seed, so that it is necessary to examine 
ripe fruits under a lens, preferably in cross section. 
The Family has been divided into nine Tribes, six of which are represented in 
the British flora. The Hydrocotyle^ have their flowers in simple umbels and their 
fruit compressed laterally , i.e. in a direction parallel to the commissure, so that that 
surface of junction between the carpels is narrow. Hydrocotyle , the name of which 
was coined by Tournefort from the Greek vS up, hudor , water, and KorvXr /, kotule, a 
dish, with reference to its peltate leaves, is the only British genus in this Tribe, and 
is represented only by the one species, Hydrocotyle vulgaris Linne, which is more 
generally known as Marsh Pennywort than by any other popular name. The 
genus comprises some seventy species, all small perennial plants, mostly creeping, 
with the peltate and more or less entire leaves which distinguish them at once 
from the rest of the Family. 
Our species has a long trailing stem, so that in marshy ground it is often massed 
together in broad patches. The leaves are erect, one or two springing from each 
node of the stem, and they are borne on slightly hairy stalks which are considerably 
longer than the peduncles. Their blades are glabrous, rather fleshy, nearly circular, 
doubly crenate, and from one to two inches across. The little axillary umbels hidden 
under the leaves consist of from three to six flowers, but very often elongate 
proliferously at the centre into a second cluster. As the individual flowers are almost 
sessile, the inflorescence is almost a capitulum rather than an umbel. The flowers 
are greenish or tinged with pink, and the little fruits consist of two much-flattened, 
nearly circular carpels, dotted over with reddish resinous points and with two ridges 
down each surface. 
This harmless and rather ornamental little plant has suffered much opprobrium 
which can hardly be said to be altogether merited, being often known as White Rot , 
Sheep-rot , Sheep-killing Penny Grass , or Flowkwort, because it was supposed to produce 
rot in sheep. The explanation of this popular belief is that the liver-fluke, the 
parasitic worm that causes the fatal disease in question, passes one stage of its 
development in the bodies of small freshwater snails which live upon the leaves of 
various marsh-plants and are eaten by sheep with these leaves. 
As might be anticipated in the case of such inconspicuous flowers as those of 
this species, self-pollination appears to be at least possible, since, although the flower 
is protandrous and the anthers open in succession, the stigmas are mature before the 
last of the five anthers bursts. 
