ASCLEPIAS 549 



ASCLEPIADACEJE, OR MILKWEED FAMILY 



A small family of perennial herbs, comprising about 85 species. 

 They are most abundant in North America. The leaves are opposite 

 or whorled; the flowers usually have a 5-parted corona between the 

 corolla and stamens, which is adnate to one or the other; the fruits 

 are follicles. The anatomical characters resemble very closely those 

 of the Apocynacese. Laticiferous cells have the same general char- 

 acters and are distributed throughout the plants, as in the Apocyna- 

 cese. The fibrovascular bundles are of the bicollateral type. Cork 

 originates either in the epidermal layer or sub-epidermally, the cells 

 being mostly thin-walled and tabular. In the pericycle occur either 

 solitary or small groups of bast fibers. The latter are not found in 

 the secondary cortex. The walls of the tracheae and wood fibers are 

 provided with either simple or bordered pores. Calcium oxalate is 

 secreted in the form of solitary crystals or rosette aggregates. Both 

 the glandular and non-glandular hairs are either unicellular or 

 uniseriate. 



Asclepias. PLEURISY ROOT OR ORANGE MILKWEED ROOT. 

 The rhizome and roots of Asclepias tuberosa (Fam. Asclepiadacese), 

 a perennial herb (Fig. 236) growing in dry or sandy soil in the eastern 

 United States and from Arizona to Texas. It is distinguished from 

 all the other species of Asclepias in not having any laticiferous cells. 

 The flowers are orange colored and very beautiful. The root grows 

 deep in the soil and is usually collected in the fall. The larger fusiform 

 rhizome and roots are cut longitudinally to facilitate drying. The 

 drug should be carefully dried and preserved. 



Description. Usually in broken pieces, frequently split longi- 

 tudinally; when entire fusiform, from 5 to 15 cm. in length and 

 from 0.5 to 3 cm. in thickness; externally light orange-brown, deeply 

 longitudinally furrowed, having a few short roots and root scars; 

 occasionally somewhat annulate in the upper portion, crown with 

 several short stem bases and occasionally deep elliptical scars; frac- 

 ture of thin pieces short, of thicker pieces tough; inner surface having 

 a thin outer layer of orange-yellow stone cells; cortex thin, whitish; 

 xylem, slightly radiate and having numerous cavities due to the 

 shrinking of the parenchyma and medullary rays; pith wanting 

 except in the rhizome portions, where it is whitish and contains 

 numerous yellowish stone cells; odor slight; taste starchy, slightly 

 bitter and acrid. 



Inner Structure. Cork of several layers of thin-walled, tan- 

 gentially elongated, slightly lignified cells, which are usually wanting 



