826 MELIACE &. 
_ affect it, but it precipitates with oxalate of ammonia. It makes — 
a weak mucilage, and is of little value. 
Microscopic structure—According to the Pharmacographia, 
the suberous coat consists of numerous layers of ordinary cork 
cells, which cover a layer of nearly cubic sclerenchy matous cells. 
‘This latter, however, is not always met with, secondary bands | 
of cork (rhytidoma) frequently taking its place. The liber is 
commonly built up of strong fibre-bundles traversed by 
narrow medullary rays, and transversely separated by bands of 
parenchymatous liber tissue. Crystals of oxalate of calcium 
* occur in the parenchyme more frequently than the small glo-- 
bular starch grains. |The structure of the bark varies consider- 
ably according to the gradual development of the secondary 
cork bands. We have examined the fresh bark and find that 
_ it agrees with this description. 
Chemical composition. An ified of the bark gives with 
perchloride of iron a blackish precipitate ; the infusion is not 
altered by tannic acid or iodo-hydrargyrate of potassium. If 
the inner layers of the bark are alone exhausted with water, — 
the liquid affords an abundant precipitate with tannic acid; 
but if the entire bark is boiled in water, the tannic matter 
which it contains will form an insoluble compound with the 
bitter principle and prevent the latter being dissolved. 
_ (Pharmacographia.) According to Broughton, the bitter 
principle of the bark is a neutral resin, having scarcely any 
definite reactions. It may be obtained by exhausted the | 
_ bark with alcohol of 60 per cent., precipitating the filtered 
- tincture with water, and purifying the precipitate by solution 
successively in benzene, carbon bisulphide, dry ether, and | 
finally, - absolute alichot It is soluble in strong boiling 
solutions of the fixed alkalies, from which acids precipitate it 
apparently unaltered. It does not form definite compounds 
acids or with bases, but on treating it with nitric acid 
and precipitating with water, a nitro-derivative is obtained, — 
having the composition C58 46 (NO*)* O11, hence the — 
ceapowe of the bitter principle is inferred to be C36 H5° O'!, 
