50 POWDERED VEGETABLE DRUGS 



(Parmelia, Physcia) are present ; more rarely also remnants of f ruticose 

 forms (Usnea). The cinchona barks are especially rich in lichens, 

 presenting a mottled appearance, due to the presence of the crustose 

 thalli, through which the apothecia are distributed. Some of the smaller 

 more rudimentary lichens closely resemble some of the spot fungi. 



The presence of lichens is not indicative of a poor quality of the 

 drug. If present in considerable numbers there is no doubt that a 

 portion of the active constituents of the drug are destroyed, due to the 

 life activities of the lichens. Since lichens are less parasitic (saprophy- 

 tic) in their mode of living than fungi, they do abstract correspondingly 

 less of the assimilation products of the host plant. The host plant 

 serves principally as a physical support rather than a source of food, 

 though there is little doubt that some food is supplied to the lichen by 

 the host plant in addition to the assimilation products prepared and 

 supplied by the symbiotic algae (gonidia). In any case, lichens occur 

 only sparingly upon a comparatively few stem barks and need cause 

 no concern to the pharmacist as regards the value of drugs. They 

 are principally of botanical interest, and, as already indicated, they 

 are of occasional diagnostic value. 



2. ANIMAL PARASITES 



The most destructive pests to vegetable drugs are certain animals 

 which feed upon the drugs in containers and store-rooms. Some drugs 

 are more readily attacked than others. Those rich in starch, sugar 

 and inulin, are especially liable to attack, no matter how poisonous 

 they may be, as strophantus, belladonna root and aconite root. 



These parasites belong principally to the insecta and aracbnida. 

 Of the insecta the most common is Sitodrepa panicea. This is a small 

 beetle about one-fourth inch in length, of a dull brown color. The 

 insect passes its entire existence among the drugs. The larva hatched 

 from the egg is a light colored grub, which feeds very voraciously upon 

 the drug for several weeks, then pupates (resting stage), and finally 

 develops into the sexually mature insect (imago), which also feeds 

 upon the drug and lays the eggs from which a new generation springs. 

 Sometimes almost the entire drug is destroyed, leaving only a thin 

 outer shell, which crumbles to pieces under the slightest touch. 



There are a number of other insect parasites which may be found 

 among drugs. Lasioderma serricorne resembles Sitodrepa in form and 

 habits. Ptinus brunneus is somewhat larger with long antennae; 

 it is similar in habits, but seems to show some preference for leaves 

 and leafy herbs and powders. Other comparatively rare insect para- 



