252 NATURAL HISTORY OF PLANTS. 



few layers of uncoloured cells in radiating series under the epidermis 

 of the stems. More internally, the parenchyma, filled with 

 chlorophyl, is mingled with a mass of larger and uncoloured cellules. 

 In the course of the second or third year, these latter become more 

 compact, and their coat increases in thickness, whilst the interposed 

 cells become dry and dark coloured. The suberose layer thickening 

 still more during the fourth and fifth year, the epidermis bursts, and 

 the mass of cork thenceforth increases in thickness, a new layer being 

 formed each year. The annual zones are separated by interposed 

 layers of periderm, of a deeper colour. At the age of from ten to 

 fifteen years, vertical rectangular plates of this cork, called male^ are 

 cut, under which are found the liber and deep portions of the cortical 

 parenchyma. Outside of this, layers of cork are produced and cut 

 every seven or eight years ; the quality of this cork, called female^ 

 is very superior. This work is carried on principally in the south- 

 west of Europe (particularly France), and in the north-west of Africa. 

 Another Mediterranean species, Q. coccifera^^ nourishes the Kermes, 

 formerly celebrated in industry as a dye, and in medicine forming 

 the base of the famed Alkermes confection. The gall-nuts of the 

 Levant, the best employed in therapeutics and the arts, are developed 

 after the puncture of a hymenopterous insect, Dijjlolejns gallce 

 tinctorice ; the female of which pierces the scarcely formed buds of 

 Q. lusitanica^'^ a Mediterranean species, to deposit her eggs in the 

 interior. The bud becomes hypertrophic by the accumulation of a 

 large quantity of tannin and fecula, on which the young insect, 

 emerging from the egg, feeds, until it pierces the gall and comes 

 forth in a perfect state. Many other Oaks, especially the Green 

 Oak, Q. Tohur, and, in the south-west of France, the Tauzin Oak,^ 



d. Entw. d. Baiimrinde. Berlin (1853). — C. DC. Med. v. 581.— Berg, et Schm. Bar&t. Off. Gew. 



Be la Production Nat. et Art. du Liege {Mem. t. xxix. i. — Q. CanariensisW . Enum. Hort. Berol. 



Soc. Gen. xvi.). — Duchtre, Elem. 157. 975. — Q. rigida C. Koch, Linncea^ xix. 15. — Q. 



1 L. Spec. 1413.— Webb, It. Bispan. 15.— Mirbeckii Dur. Rev. Bot. ii. 426.— Q. hrwhy- 

 A. DC. Prodr. n. 104. — Guib. Brog. Simpl. ed. carpa Kotsch. — Q. Cypri Kotsch. — Q. Pjaffin- 

 6, ii. 289. — Hayne, Arz. Gew. t. 44. — Q. pseudo- ge?-i Kotsch. — Q. Gallce turcicce off. 



coccifera Desf. El. Atl. ii. 349. — Boiss. Voy. Esp. ^ Q. Toza Bosc, Jonrn. d'Hist. Nat. ii. 155, 



578, t. 165.— Q. Mesto Boiss. op. cit. t. 166.— t. 32, fig, 3.— A. DC. Prodr. n. 4.— Grex. et 



Q. Auzandri G^^^. et GoDn. El. de Er.n\.\l%. Godr. Fl. de Er. iii. 117.— Q. PyrenaicuW. 



2 Lamk. DiW.i. 719(1783).— Webb, 0«.irisj9. Spec. iv. 451.— Lamk. 111. t. 779.— Q. Nigra 

 11.— A. DC. Prodr. n. 19.— Q. Infectoria Oliv. Thore, Land. 381 (not L.).— Q. Tauzin Pers. 

 Voy. i. 252, t. 14, 15. — Guib. Brog. Simpl. ed. Eiichirid. ii. 571. — Q. stolonifcra JjKP.Abr. 582. 

 6, ii. 282, fig. 418.— Mer. et Del. Bic^. Mat. —Q. brossa Bosc. Mim. 15. 



