792 



THE AMERICAN NATURALIST [\^ol. XL 



which are most frequently affected by loco disease. Cattle occa- 

 sionally acquire the loco habit, but the cases are comparatively 

 rare. In certain parts of Montana the habit became so wide- 

 spread among horses that the raising of them was abandoned until 

 the locoed animals were disposed of and other horses which had 

 not the loco habit had been imported" (p. 89). "During the 

 ])rogress of field work in Montana in 1900, about 650 locoed sheep 

 and 150 locoed horses were seen " ^ (p. 90). 



Mechanically Dangerous Plants. — There occur in Montana 

 occasional losses of stock from plants acting mechanically. For 

 example, the sharp-barbed awns of the porcupine grass (SHpa 

 spartea) and squirreltail (Hordeum jubatum) when the plants are 

 maturing, separate, and entering the mouth, throat, eyes, and ears 

 of stock, affect the tissues and give rise to ulcers which cause intense 

 suffering and necessitate killing.^ Similarly the corn-stalk disease 

 is sometimes attributed to malnutrition or impaction of the 

 alimentary canal. 



In this connection may aUo be cited an observation recorded 

 by 'riiistl(>t()n-I)yer' wliicli happens to bear ujxjn the life of goats. 

 ••'rhriiitro.luctioiK.f the sweet briar into Xew South Wales, Austra- 

 ha, in many jjarts of wliich it is naturalized, affords a striking 

 illustration of the mode in which the balance of nature may be 



disturbed in a wholly unforeseen way The fruit of the sweet 



Ijriar (Rosa ruhiginosa) consists of a fleshy receptacle lined with 



silky hairs which contains the seed-like carpels The hairy 



linings of the fruit caused the death of a number of goats by form- 

 ing hairy calculi, which mechanically occluded the lumen of the 

 bowels. These goats were put on the land with the idea that they 

 wouhl VAX down the l)nurs and ultimately eradicate them, but 

 the l>riars •■nine out t.<->t and cracUcatcl tlie goats. The cattle 



