GALLS 169 



as that contained in oak barks (Quercus), catechu (Acacia), kino 

 (Pterocarpus), rhatany (Krameria), canaigre (Rumex), tormentilla 

 (Potentilla) and mangrove (Rhizophora). 



For a full discussion of the nature of tannin, its chemical proper- 

 ties and distribution in plants, consult Kraemer's Applied and Eco- 

 nomic Botany, pp. 202-210. 



Gallic Acid crystallizes in silky needles or prisms which are 

 inodorous and possess a faintly astringent taste. It is sparingly 

 soluble in cold water, but soluble in alcohol; forms crystalline com- 

 pounds with the alkalies, alkaline earths, lead and copper salts; and 

 gives a bluish-black precipitate with ferric chloride, which is soluble 

 in acetic acid and loses its color on boiling. 



Allied Plants. On a number of species of Rhus, galls due to the 

 stings of certain plant lice (Aphis) are formed, as Chinese galls, formed 

 on Rhus semialata; Japanese galls, formed on R. japonica, and Amer- 

 ican Rhus galls, formed on Rhus glabra and R. hirta. Chinese and 

 Japanese galls are very rich in tannin, and as they contain less color- 

 ing matter than the oak galls are used in the manufacture of gallic 

 acid. They are more or less irregular in shape, but somewhat ovoid, 

 more or less tuberculate, grayish-brown, very hairy, light in weight, 

 brittle. The wall is about 1 mm. thick, and the cavity contains the 

 remains of numerous insects in the form of a grayish powder. 



The powder of Japanese or Chinese galls is grayish-green and 

 contains numerous non-glandular hairs; starch grains from 0.015 

 to 0.040 mm. in diameter; rosette aggregates of calcium oxalate, 

 from 0.015 to 0.25 mm. in diameter; occasional fragments of tracheae 

 and laticiferous cells. Mounts in glycerin may show separation of 

 acicular crystals. 



American nutgalls are formed on Quercus coccinea and Q. imbri- 

 caria by Cynips aciculata. When fresh they are globular, 1.5 to 3 

 cm. in diameter, and of a yellowish, somewhat mottled color. On 

 drying they become yellowish or dark brown and much shriveled 

 externally. Texas nutgalls are formjed on the live oak (Quercus 

 virens) and yield 40 per cent of tannic acid. California oak balls 

 are excrescences on Quercus lobata and are about 5 cm. in diameter, 

 and said to contain considerable tannic acid. 



Other tannin-yielding plants are found in the following families: 

 Combretacese, Leguminosae, Myrtaceae. 



CASTANEA. Chestnut Leaves. The leaves of Castanea den- 

 tata (Fam. Fagacese), one of the most useful and beautiful trees of 

 the forests of eastern North America. The leaves are usually gath- 

 ered in the early fall and carefully dried. It is very probable, how- 



