WOOL. 195 



The other genus of plants is styled Medicago (Leguminosae), the 

 principal species of which are maxima, denticulatum, minimum, and 

 maculatum. These bur weeds have spiral or conical seed-pods covered 

 with densely-set horny spines, which readily hook into the woolly cover- 

 ing on the sheep's back. 



Fig. 119 shows a branch of the bur weed Xanthiam spinosum with 

 the leaves attached to the parent plant. 



The leaves are broad, without spines, and the fruits are gathered into 

 ovate heads, which are crowded with hooked spines. These readily 

 adhere to the wool of sheep. The photograph is taken from a plant 

 growing in the herbaceous department of the Royal Gardens, Kew. 



Fig. 119. Bur weed. 



The wool used by hatters is often infested by the spiny involucres of 

 the bur weed, which are got rid of in carding. 



Fig. 120 shows the spinose character of the spiral bur fruit of the 

 Medicagos. 



Fig. 121 shows the spines magnified under the microscope. 



A bur cleaner has been devised by Garnett's of Cleckheaton, York- 

 shire, and is much used in the woollen mills of Yorkshire. 



Fig. 122 is an example of burry wool infested with various impurities, 

 such as burs, spines, and other vegetable structures that are difficult to 

 remove from the wool, except by a process of carbonising. A machine 

 is often used, by which the burs are released, and cleaned wool passed on 

 withour impairing the colour. 



Shawl Wool. This is the fine wool of Tibet. It is thus referred te 



