President’s Address lxxxi 
style ; those of Bidens bipinnata are provided with two sharp points, 
barbed like a fishing hook; the persistent calyx of Agrimonia and Acena, 
the capsules of Triwmfetta, and the fruitlets of Torilis Africana, Echino- 
spermum Lappula and Cynoglossum, are covered with sharp hooks similar 
to those on the English burdock. 
Two troublesome plants, the burweed (Xanthiwm spinosum) and the 
little burweed (Medicago Aschersoniana), have been spread over the globe 
on account of such excellent armament on their fruits, necessitating 
special legislation against the former in this country as well as in many 
others. The klitsgrass (Panicum verticillastre) bears such hooks on its 
spikelets, and many a wanderer in the central and northern districts 
has experienced the annoyance it causes, as it prefers the shade of 
trees for its habitat. The steek-grasses have a most unpleasant way of 
spreading their seed, and are the cause of considerable trouble and loss 
to the sheep-farmer. They belong principally to two genera. The 
flowering glume of Aristida, e.g., A. congesta, is stipitate, and provided 
with a feathery awn. The ripe seed does not fall out, but remains 
enclosed in the glume, as is the case with oats. When the spike is 
touched by a passing animal, the finely-pointed stalk of the glume 
breaks off and easily penetrates into the hairy coat of the animal. It 
is needless to say that the presence of these spikelets in wool lowers its 
value considerably. More dangerous is Andropogon contortus (see Figs. 
9 and 10). 
The basal stalk as well as the outer glume are covered with short, 
stiff, and reversed hairs, and the flowering glume is changed into 
a long twisted awn. If the sharp point of the spikelet has once 
reached the skin of an animal, it will force its way in until the seed is 
broken off by force; for the twisted awn contracts and loosens its 
twists according to the amount of moisture in the air, and consequently 
bores the seed in, while the stiff reversed hairs prevent its backward 
motion during the intervals. The whole process is very similar to that 
by means of which Pelargonium buries its fruitlets in the ground. If 
the sheep endeavours to get rid of the irritating seed by rubbing against 
bushes or stones, it only forces the seed deeper into its skin, just as the 
bristles of the prickly pear will penetrate deeper and deeper on account 
of the reversed barbs. The effect on the sheep is so serious that they 
often die, especially when young. 
Some other plants attack the feet of animals for the same purpose. 
The little nuts of Tribulus terrestris and T. Zeyhert are armed with 
strong sharp spines, which easily pierce the foot that treads on them. 
The fruitlets of Emex centropodiwm are quite similar, both having 
deserved thereby the Dutch designation of ‘Duiveltjes.’ The fruitlets 
of Tetragonia dimorphantha and the schizocarps of Arctopus echinatus are 
