THE ESSEX FIELD CLUB.
99
ceptions most weeds occur on occasion on all types of soil, but many are
now frequent and more abundant on some soils than on others.
A. Weeds of General Occurrence.
These are usually abundant on any and every soil, and are provided
with very efficient methods of propagation by seeds and underground
parts. Many of the worst weeds are included in this group, e.g., bent-
grass, Chickweed, curled dock, creeping thistle, shepherds purse, groundsel,
fat hen, knotgrass, etc.
B, Weeds of Heavy Land.
Not at all well distinguished from those of ordinary loamy soil; very
few are characteristic other than stinking mayweed, hoary plantain, corn
buttercup and cut-leaved geranium, and to some extent black bent
(Alopecurus agrestis).
C. Weeds on Chalky Soil.
The old idea of chalk-loving and chalk-hating plants does not alto-
gether hold good. The dominant chalk-weeds of some districts are absent
or rare in other chalk areas. The most generally characteristic weeds are
white mustard, toadflax, mignonette, lamb's lettuce and hardhead.
D. Weeds of Sandy and very Light Land.
These afford the chief instance of weeds indicating a particular con-
dition of soil; in this case, deficiency of lime. Sheep's sorrel, annual
knawel (Scleranthus annuus) and Spurry occur in abundance.; corn
marigold (Chrysanthemum segetum) appears to come in the same category.
ASSOCIATION WITH CROPS.
This is less clearly marked than the association with soils, but is quite
distinctive. The habit of the crop is largely the determining factor, the
time of sowing and methods of cultivation and sowing also playing a part.
A. Common Weeds of General Occurrence.
Usually found with all crops.
B. Cereals.
If stand is thin, low-growing weeds, as mayweed and lady's mantle,
are able to flourish and cover the ground. If crop is heavy, then tall plants
can flourish, e.g., wild oat, corn cockle, Sowthistle, etc.
C. Roots.
The late sowing and drastic cultivation of the crop prevents many
weeds from flourishing. Chickweed is one of the most characteristic
weeds, as it clings round the roots and escapes destruction.
D. Clover, Tares, etc.
Most weeds are smothered out by the crop, but special varieties are
usually introduced with this crop, including field madder, geranium spp.,
wild pansy, carrot, ribwort plantain and campion.
The results so far obtained are based upon records from fields from a
limited number of counties and geological formations. Final conclusion
cannot be drawn without wider experience, as local conditions may have