Agricultural H'eeds. 
373 
of the question to effect their destruction during the growth of the 
crop. The only thing to do is to destroy their shoots, being careful 
to attack their rhizomes in the fallow. This, indeed, is true with 
respect to deep-rooted weeds in general — they can only be 
crijiplcd during the growth of the crop, whereas the due prc- 
jjaration of the land should include measures for their destruction. 
Parasitic Plants. — The growth of parasitic weeds in their 
earlier stages is a subject still involved in considerable mystery ; at 
the same time there can be but little doubt that the broomrapes 
and dodders are introduced in tlie seed : and as there appears, for 
the most part, far less care taken in the growth and collection of 
foreign than of our native seeds, it will be found that exotic 
clover or flax-seed is sure to bring these parasites to a greater or 
less extent, and so destructive are they to the crop, that occasion- 
ally whole fields of clover may be seen greatly injured by the 
Orobanche elatior (tall broomrape) and 0. minor (smaller broom- 
rape), whilst other fields are in like manner attacked by the 
Cusciita Europaa (dodder). The seeds of the broomrapes are 
very small and numerous, and, becoming mixed with the clover- 
seed, from which it is difficult to separate them, they are thus dis- 
tributed wherever the seed for the crop is sown, and hence broom- 
rapes will usually be found spread over the whole surface of a 
clover-field. However, the stem being upright and tolerably con- 
spicuous, it is soon detected. With the dodders the case is very 
different, as their seed is of tolerable size, so that usually only 
a few of them would be mixed with the seed for the crop ; ger- 
mination, therefore, would commence at but few places, which we 
may term centres. Their growth, however, is not upright, the shoots 
being long and flexile, and they destroy the plant upon which 
they fasten by sending rootlets into its stems, from every point 
of contact, which suck up its juices. By these means the parasite 
extends its own growth still farther, destroying in every direction 
around the centre from which it started, and spreading itself over 
a large surface in an incredibly short space of time. Now it is 
obvious that, in treating these two cases, we must act in accord- 
ance with the observed facts. Tlie broomrapes, for example, 
cannot be hoed, as they attach themselves on the very roots of 
the clover ; and besides, this is not a crop that can be so treated. 
Tliey can only be destroyed by pulling, and this is easily done, 
as the bulbous base separates very readily from the clover-root. 
The dodder must be attacked by destroying it at its centres, as 
soon as it is observed, by either mowing or pulling, as the case 
may be ; but in no case can we, as honest men — who should do 
as we would be done by — let the affected crop stand for seed, as 
is too often done with such crops of clover, inasmuch as on 
the physiological principle of arrested development tending to 
