34 



diameter being only 1.2 m.ni. Usually the seed measures about 

 1 m.m. In color it is dull gray and the surface has many small 

 papilla-like projections. 



The epidemial layer of the seed coats is sufficient for its iden- 

 tification. The cells of this layer are very characteristic, being 

 large, roughly polygonal in shape, with a sharp saw-tooth out- 

 line. The walls are highly refractive and show distinctly. In 

 the center of each cell there is a rounded protuberance which 

 shows dark under the microscope and gives the roughness to the 

 seed. Besides this large hump there are many small projections 

 which appear as dots under the lens. (Fig. 2G.) 



MISCELLANEOUS WEED SEEDS. 

 JIMSON WEED, JAMESTOWN WEED. 



(Datura stramonium, L.) 



This weed occasionally occurs in feeds as an impurity and is 

 very harmful on account of the alkaloid which it contains. It 

 is an easy matter to identify this seed as its external markings 

 are characteristic. 



It is from 3 — 4 m.m. long and from 2 — 2.75 m.m. broad, in 



Figure 27 

 Fig. 27. Jimson Weed. 



shape resembling a lima bean. The color of the seed varies from 

 brown to black, and to the naked eye the surface appears to be 

 covered with small depressions of a roughly pentagonal form, 

 giving a wrinkled appearance to the seed. Under the microscope 

 the surface is found to be made up of cells with extremely sinuous 

 outlines and very irregular in size and form. These features are 

 sufficient for a diagnosis of this seed. (Fig. 27.) 



