GALLiE HALEPENSES. 5117 



central cavity, sometimes nearly | of an inch in diameter, which served 

 as a dwelling for the insect, is lined with a thin hard shell. If the 

 insect has perished while still very young, the central cavity and the 

 aperture contain a mass of loose starchy cellular tissue, or its pulverulent 

 remains ; if the insect has not been developed at all, the centre of the 

 gall is entirely composed of this tissue. 



Microscopic Structure— The cellular tissue of the gall is formed 

 in the middle layer of large spherical cells with rather thick porous 

 walls, becoming considerably smaller towards the circumference. The 

 outermost rows are built up of cells having but a very small lumen and 

 comparatively thick walls, so that they form a sort of rind. Here and 

 there throughout the entire tissue, there occur isolated bundles of vessels 

 which pass through the stalk into the gall. Towards the kernel, the 

 parenchyme gradually passes into radially-extended, wider, thm-walled 

 cells, the walls of which are marked with spiral stria. The hard sh>l 

 of the chamber 1 is composed of larger, radially-extended, thick-wallcd 

 cells, with beautifully stratified porous walls. On the mner side of this 

 shell there are found, after the escape of the insect, the remains ot the 

 starchy tissue already mentioned, which originally filled the chamber 

 and had been consumed by the insect as nourishment. 



The Darenehvme-eells outside the shell contaui chlorophyll and 



parenchyme-cells outside 

 tannin; the latter is in transpai'ent. 



la^bcs 



uaiiuui; tne lauter is in wauspajLeiii^, »^uxv/«xxv.v^>^, r, i°- i u^i 



insoluble in benzol, but dissolving slowly in water, qmckiy in alconoi. 

 Thin slices soaked in glycerin appear after some time covered ^^ .ti 

 beautiful crystals of gallic acid. The thlck-walled eel s (^tonc-H^ 

 and the neighbouring striated cells, are rich in ^ctahedi-a of calOT 

 oxalate. The tissue of the gall situated withm the shell of t "ck- ^1 ^d 

 cells contains starch in large, compressed, mostly ^^P^^^^^^^^f'^^^'L' 

 also isolated masses of browS resin. Besides these, there appeals to be 

 in this part of the tissue an albuminoid compound. 



Chemical Composition -The rough taste of 8|"« i!^,?"? ^. 

 their chief constituent. Tannic or GaUo-tanmc Acid, ^ u u, u 

 gg;(^H)TOOH ) ^^^ ,f , ,,^erous family of substanc - 

 OHOH)CO_ j ' /V . . ,.,. T..^nic matter 



which vegetables owe their astringent properties. J^P^^f J^J^j, 1, 

 long supposed to be of one kind, namely that [^"fj^^jf^^aiffeLt 

 but the researches of later years have proved \\Vtrm wi/o-frrwvuc 

 plants to possess distinctive characters: hence Vf\P.^iiy derived, 

 acid to distinguish that of galls, from which ^^ ;\P;^^" W^^, ^3^3^ 

 It was however shown by Stenhouse as far back P , J.^^^^^^ 

 again in 18G1, as well as by still more recent "^^f^'^^^^^^^^J ^f Bhm 

 that the tannic acid found in Sicilian «""'^^^f .'"^ j,^ I873 came to 

 Coriaria L., is identical with that of oak galls l^o^ ^^ ^^ 



the same nn^Pln^^.n The best oak galls yield of this acia. 



same conclusion. The best oak g 

 To per cent. 



^GY cent. _ J formed to the extent of 



Gallic Acid is also contained in galls lea J, 1 g also been 



about S per cent. Free sugar, resin, protem-substances, 



found. Neither gum nor dextrin is present. ,v>..rr>;pal sub- 



, . . i^ rivpino' of new chemical suu 

 Commerce-The introduction into chemg oi 



irf . T. XI • ■ ^ inn. des Scknc^' A«^, -Bot. xix. {i^-yv 



Louche protedrice of Lacaze-Duthiers— ^^^ . 

 ^echcrches jioitr servir a Vlddoire dcs [jalles. ->t>-«>^ • 



