MICROSCOPICAL EXAMINATION. 81 



very characteristic. The epidermal cells are polygonal in shape, and 

 the walls have saw-tooth outlines, the teeth having a length equal to 

 about one-third of the cell diameter. (Plate IV, fig. 1.) They resem- 

 ble the cells of the Saponaria officinalis L., but are more regular in 

 outline and not so large, though the thickness of the walls is some- 

 what greater. The middle lamella in well-cleaned material often 

 appears as a dark line in the middle of the cell walls. The second 

 layer of importance is one consisting of rectangular cells with nearly 

 dear walls, but brown contents. (Plate IV, fig. 2.) They are found 

 on the inner side of the seed coats near the hilum and extend for a 

 short distance over the radicle. They recall in appearance quite 

 strongly the pigment cells of flaxseed, but are not so regular and are 

 smaller, though with thicker walls and coarser pits. 



JIMSON WEED. 

 Datura stramonium L. 



The seeds of jimson weed are like the lima bean in shape, 3 to 3.75 

 mm in length, and of a dark brown or black color. The surface is 

 covered with small depressions, giving a rough appearance to the seed. 



These examinations lead to the conclusion that fortunately this 

 poisonous seed is not often found in cattle foods. Its identification 

 is a simple matter, for the seed coats have very characteristic mark- 

 ings. The coats consist of cells of very sinuous outlines, the indenta- 

 tions often extending nearly to the center of the cells. (Plate IV, 

 fig. 4.) The walls are highly refractive to light, and though quite 

 easily cleared are difficult to represent very satisfactorily in a 

 photograph. 



PLANTAIN. 



The structure of the various species of plantains fs much alike, 

 though it is possible to identify them. The seeds in general resem- 

 ble miniature canoes, although in the case of Plantago major L. both 

 sides of the seed are somewhat convex. 



One interesting difference between the species is in the position 

 of the cotyledons in the seed. In some of them the cotyledons are 

 placed ventrally and dorsally, while in others they occupy a right- 

 and-left position. 



The leading characteristics of the four species which are quite 

 frequently found in stock foods are as follows : 



BRACTED PLANTAIN. 



Plantago aristata Michx. 



The seeds of this species are from 2 to 3 mm in length and about 

 half as wide, of a medium brown color, and have a dull surface. At 

 the middle there crosses the seed transversely a slight depression 

 readily seen with a hand lens. 

 12228 Bull. 10807 6 



