191 i.J The Stemless or Dwarf Thistle. 907 



From these observations it may be concluded that cake 

 such as that used is harmless. Variation due to idiosyncrasy 

 is possible, and a cake of 0*05 per cent, would in an 8-lb. 

 feed give 28 grains of prussic acid, equal to a 4-lb. feed of 

 Java beans showing o'i per cent. acid. 



There seems no ground to suppose that hydrocyanic acid 

 is cumulative. Indeed, for a poison so volatile and easily 

 eliminated this would not be anticipated. Similarly when 

 gradually developed hydrocyanic acid could probably be 

 taken in larger quantities than would kill in one dose. The 

 general evidence of our experiments is against the supposi- 

 tion that tolerance or habituation is established, but one 

 cannot regard this as definitely negatived. 



Poisoning by giving linseed has been known and recorded, 

 and our results cannot be taken as absolutely exclusive of the 

 possibility with cakes, especially with sheep. In this con- 

 nection a test on sheep with a 0*05 per cent, cake and a deter- 

 mination of the toxic dose of the pure drug would be most 

 desirable. 



The Stemless or Dwarf Thistle (Cnicas acaulis, Willd.), is 

 sometimes termed the Chalk Thistle from its habit of growing 



freely in pastures over chalk. It may 

 The Stemless or , « u 



Dwarf Thistle. once recognised by its spreading 



rosette or tuft of very prickly smooth 

 leaves, its almost stemless or sessile flower-heads, and its 

 extensively creeping rootstock (See plate). It is a perennial 

 which sometimes occurs plentifully in dry pastures over gravel 

 and chalk in the southern and central midland counties of 

 England. The rosettes of leaves destroy the patch of herbage 

 which they cover, and when the weed is plentiful, extensive 

 damage may be done. 



The creeping rootstock and almost stemless character of 

 this thistle combine to make its eradication extremely difficult, 

 for it is a perennial which during the summer months manu- 

 factures a large amount of food material in the leaves and 

 stores it below ground in the root system. It is not tall 

 enough to be cut with the scythe or similar implement, and 

 it sometimes occurs in such numbers that continual spudding 

 is a most tedious and expensive operation. Spudding, how- 



