SCIENCE AND: INDUSTRY. 
Floods are, perhaps, responsible for the spread of weeds a great 
deal more than the normal water-ways. Flood waters cover ground 
which is hard and baked at the end of a long summer, and on which 
dried plants with their ripe seeds are’ lying about in Hundreds) These 
are picked up and rushed along by the force of the water, which, when 
it recedes, drops the seeds and leaves the ground in an ideal condition 
for their eermination. The flooding of the Murray has been respon- 
sible for the crossing of numerous weeds from one State to the other— 
the seeds could never have blown right across the river, and could not 
have been carried oyer in any quantity in any other manner. St.’ 
John’s Wort (Hypericum perforatum) has been spread down the Ovens 
River in the silt from the dredging which is carried on to such an 
extent there. Whole plants are’ embedded in the mud-and carried 
down stream. Heavy rain will also assist in scattering seeds for short 
distances, more particularly on sloping ground. 
ANIMALS AND Brirps. 
Animals and birds effect the dispersal of weed seeds over rather 
wider areas than either wind or water. Their action may be either 
active or passive according to the nature of the seed. Many fruits 
and seeds develop special devices to enable them to cling to the hair, 
fur, or feathers of any passing animal or bird, which may carry them 
for quite long distances. The devices which enable the seeds to cling 
are usually in the nature of hooks or spines which cover the fruit, the 
seed, or sometimes the whole plant. Sheep’s Burnet (Acana sangui- 
sorba) is a small plant with its fruit in a cluster forming a head. Hach 
fruit contains only one seed, and is provided with four arrow-headed 
barbs, which catch on to everything (Fig. 4). When the seeds are 
ripe, the whole head is easily detached from the plant, and when the 
barbs catch onto a passing animal, the head breaks off, and is carried. 
away to be dropped later when the animal sets to work to rid itself 
of its unwelcome yisitor. 
The wool of sheep that have been feeding in pastures infected with 
this or other weeds with spiny fruit, becomes seriously deteriorated 
in value by the number of seeds dlineine to it. Some of the worst 
offenders in this way are the Bathurst Burr (Xanthium_spinosum), 
the fruit of which is covered with strong hooks (Fig. 6); Burr Clover 
(Medicago denticulata), with tecth-lke ‘attachments to the coiled seed 
pod; and Burr Grass (Cenchrus Australis), with a spiny seed. The 
awns of grasses also catch in the wool of sheep and do a good deal of 
damage (Fig. 5). In some cases, the spines and awns are so sharp 
as to do bodily harm to the animal to which they become attached. 
Sheep and horses are lamed by treading on the spiny seeds of Caltrop 
(Tribulus terrestris). These are particularly sharp and strong, and- 
they penetrate some way into the flesh, the seed breaks off, but the spine 
remains, and causes a festering sore. 
It may be the whole plant which bears the spines or prickles, 
and when these catch in anything, a part of the plant itself is broken 
off and carried to a new spot, where it takes root. This is one of the 
methods by which the great pest of Queensland, the Prickly Pear 
(Opuntia monacantha), is spread, as practically every portion of this 
plant can strike root for itself. 
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