377 
Annual Report for 1913 of the Botanist . 
off the weed and fallowing. Once seeding is permitted, the 
difficulties of cleaning are enormously increased. 
Heavy dressings of lime often effectually rid the land of this 
weed. Apparently, though, this is not an invariable specific. 
Where it fails, spraying with a 5 per cent, solution of copper 
sulphate has been recommended. The trials which we have 
made show that this kills off the younger plants and prevents 
many of the older ones from seeding. The spray is not as 
efficient, though, as it is with charlock, and there is little doubt 
that it will have to be employed for several seasons to clean the 
land at all thoroughly. _ ,. 
The red shank (Polygonum per sicarta), another tree seeding 
annual, has been reported on on several occasions. This occurs 
most frequently on moist soils which otherwise are m good 
condition. Continuous surface cultivation in the early summer 
is usually sufficient to suppress it, but where this is impractic- 
able, a spraying with a copper sulphate solution ot the same 
concentration as above gives satisfactory results. _ 
The question whether the common thistle is spread by 
means of seeds has led to some correspondence which is worth 
quoting in view of the fact that the belief still exists that 
the plant does not produce fertile seeds A member had had 
occasion to complain to a neighbour with regard to the thistle- 
ridden condition of his fields. He was told that this woul 
not affect adjacent fields because no seed was produced. 
Evidence usually quoted in support of this beliet is that 
drifts of thistledown consist solely of floats. This is true n 
the main, but the fact is overlooked that the slightest jar, as 
for instance when the floating seed settles on the ground, 
leads to the separation of the seed from the float. An e»m>- 
tion of ripe thistle-heads should be sufficient to convince 
anv sceptic that it is as well to prevent seeding. 
Broom-rape ( Orobanche minor), a parasite on clover, was 
reported as causing damage in the south of Eng'and 
ptant is not uncommon on light soils and is usually to be found 
pushing its thick brownish shoots above the soil soon after the 
removal of the first cut of clover. The tuberous base of the 
stem is attached by suckers to the clover root and obtains its 
nourishment direct from it. The seeds are dust-like and 
produced in enormous numbers. There is some evidenc 
show that they can remain in a dormant condition in the soil 
for several years. The eradication of the parasite, once it s 
established, is difficult. Probably the best procedure is to 
prevent the formation of seed by hand-pulling the 
shoots and to miss clover once from the rotation. The intro 
duction of the seeds of the pest with the clover seed need no 
be feared, since the bulk of it ripens and is distributed befoie 
