ON THE FLORA OF THE YORKSHIRE COALFIELD, 145 
poisoning their element with dyestuffs, tanpit refuse, chloride of lime, 
&e. Still I see no reason for doubting that many of the present 
of the coal country; and Hippuris, Ceratophyllum, Potamogeton 
pusillus linger here and there in mill-dams and reservoirs, with plenty 
_ of Sparganium, Veronica Beecabunga, and Mentha aquatica in water 
cuts and ditches. 
Throughout the coalfield area there isa woeful dearth of Orchids— 
such common ones as Listera ovata, and Orchis mascula are almost un- 
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‘ istrict, and in the opinion of many competent observers 
in the flagstone tracts about Bradford and Halifax too: the plants are 
of the double or garden form, and not of the depauperate wild one. 
bak composed of hard nodules interlayered with friable marls, 
ic absorbent, retaining moisture only in a small degree, but allowing 
Sil ght Of quickly ; and having in consequence a warm, dry, mad 
hire a 2» in which flourishes the richest flora of any West York- 
Tuatttict. 
oredal Rorth-western hill country of Craven is made up of the 
: Scar-limestone strata, dysyeogenous (to tina Thur- 
