Agricultural Weeds. 
371 
those tliat do come up before they have seeded that the enemy 
has been destroyed, for of those that did not germinate for want 
of air many of them only require to be brought to the surface by 
a new ph)ughing to bring them into life. Indeed, seeds of many 
weeds, as charlock, the speedwells, chick weed, and others, may 
lie dormant in the soil for incredibly long periods. Even the 
operation of hoeing stirs up seeds ; so that whilst it kills one 
crop of weeds it tends to the production of another, though 
much smaller one. 
The natural history of biennial weeds is a matter of importance 
to be studied in estimating their consequences and mode of 
extinction. An attentive observer will see that they have most 
of them long tap-roots, as is the case with the following : — 
Daucns carota, wild carrot ; Pastinaca sativa, wild parsnep ; 
Conium maculatum, hemlock ; Cardmis nutans, common musk- 
thistle ; Carduus acaulis, stemless thistle ; Senecio jacohea, rag- 
wort. To which may be added the genus Rumex ; for, although 
the species are classed as perennial plants, most of them die after 
producing seed, which they generally do the second year. 
Now the large fleshy roots of these plants are appointed as a 
store of food, which in them is formed the first year, from which 
the flower-stalks and seeds of the second year's growth can be 
perfected. Hence the roots, which are succulent and fleshy at 
the fall of the year, become spongy and shrivelled as the seeding 
process advances. Indeed, so perfectly is the seed formed from 
these tap-roots, that if taken out of the soil before the seed be 
perfect it will even then become ripe and reproductive. From 
this it follows that with tap-rooted biennial plants, as also with 
many of the large-rooted perennials, putting them in heaps as 
they are gathered and leaving them on the ground does not neces- 
sarily destroy the probability of a future crop, as the ragworts 
and thistles will ripen their seed in such situations, and these, 
by their wings, may be carried all over the farm. In the case of 
the docks also, the ripening seeds may be left behind, and thus 
form colonies for the continuation of the species. 
Perennial weeds require accurate observation of their habits, if 
we would successfully conquer them, as in many of these repro- 
duction and multiplication take place in several ways besides 
the usual one of seeds. Hence the Ranunculus repens (creeping 
buttercup) and PotentiUa anserina (silver-weed) send out scions 
which creep above the ground and afterwards root at their 
extremities, thus forming independent plants, which again, 
acting like their parents, spread tlie enemy in an incredibly rapid 
manner. The Tussilago farfara (coltsfoot). Convolvulus arvensis 
(bindweed), Triticum repens (couch), and others, increase by a 
rhizome, or underground stem, which buds and roots beneath the 
