THE JOURNAL OF PHARMACOLOGY. 



165 



(3) Wood fibers and 



tracheids ; 



(4) Parenchyma. 

 From the leaf : 



C5) Leaf epidermis with 

 stomata ; 



(6) Resin glands. 

 From the flower : 



(7) Pollen grain ; 



(8) Flower parenchyma; 



(9) Sclerenchymatic tis- 



sue from seed ; 



(10) Fat globules. 

 From all parts : 



(11) Fragments of resin. 

 The stem elements have 



already been sufficiently de- 

 scribed. The leaf epidermis 

 consists of rounded cells FlG - 4- 



rather irregular in size and shape. There is nothing characteristic 

 about them. The stomata are very numerous. They measure about 18 

 microns in width and about 28 microns in length. 



The resin glands are round to elliptical in shape, and are about 24 

 microns in diameter. They are composed of many small, angular cells, 

 regular at the periphery, but becoming irregular toward the center. 



The pollen grains are perhaps the most characteristic element of the 

 powder. They are circular or elliptical in outline, of a diameter of from 

 18 to 25 microns, and yellow in color. Their surface is beset with 

 numerous short, projecting spines. 



The flower parenchyma is very frail and transparent, here and there 

 showing a delicate fibro-vascular bundle. 



The glands from the scales of the involucre are very abundant. They 

 are of the same appearance as those of the leaf above described. 



The sclerenchymatic tissue forming the outer coat of the achenes is 

 easily recognized. It is composed of small, reddish-brown cells, arranged 

 in regular rows. 



The fat globules are colorless, spherical masses, varying in diameter 

 from 6 to 15.5 microns or more. They come from the inner portions of 

 the achene, and are only to be seen in the very finely powdered drug. 



The particles of resin seen here and there in the powder are irregular in 

 shape, yellow in color, and highly refractile. — Merck's Report. 



( To be Contimied.) 



