658 ORCHIDACEiE. 



ripened, and acquire their ultimate aroma and dark hue. They are 

 then tied together into small bundles. 



In Reunion the drying of the pods is performed since 18.57 by 

 dipping them previously in boiling water. 



Description — The fruit when fresh is of the thickness of the little 

 finger, obscurely triquetrous, opening longitudinally by two unequal 

 valves. It is fleshy, firm, smooth, and plump ; when cut transversely 

 it exudes an inodorous slimy juice, abounding in spiculse of oxalate of 

 calcium.^ It is one-celled, with a three-sided cavity, from each wall of 

 which projects a two-branched placenta, each branch subdividing into 

 two backward-curling lobes. There are thus in all 12 ridges, which 

 traverse the fruit lengthwise, and bear the seeds. Fine hair-like 

 papillae line as a thick fringe the three angles of the cavity, and secrete 

 the odorous matter, which after drying is diffused through the whole 

 pod. The papillae likewise contain drops of oil, which is freely absorbed 

 by the paper in which a pod is wrapped. That the odorous matter is 

 not resident in the fleshy exterior mass we have ascertained by slicing 

 off" this portion of a fresh fruit and drying it separately ; the interior 

 alone proved to be fragrant. 



The vanilla of commerce occurs in the form of fleshy, flexible, 

 stick-like pods, 3 to 8 inches long, and y'^ to ^ of an inch wide, of a 

 compressed cylindrical form, attenuated and hooked at the stalk end. 

 The surface is finely furrowed lengthwise, shining, unctuous, and often 

 beset with an efflorescence of minute colourless crystals. The pod splits 

 lengthwise into two unequal valves, revealing a multitude of minute, 

 shining, hard, black seeds of lenticular form, imbedded in a viscid 

 aromatic juice. 



The finest vanilla is the Mexican. Bourbon Vanilla, which is the 

 more plentiful, is generally shorter and less intense in colour, and com- 

 mands a lower price. 



Microscopic Structure — The inner half of the pericarp contains 

 about 20 vascular bundles, arranged in a diffuse ring. The epidermis 

 is formed of a row of tabular thick-walled cells, containing a granular 

 brown substance. The middle layer of the pericarp is composed of 

 large thin-walled cells, the outer of which are axially extended, while 

 those towards the centre have a cubic or spherical form. All contain 

 drops of yellowish fat and brown granular masses, which do not decidedly 

 exhibit the reaction of tannin. The tissue further encloses needles of 

 oxalate of calcium and prisms of vanillin. 



On the walls of the outer cells of the pericarp ^ are deposited spiral 

 fibres, which occur still more conspicuously in the aerial roots and in 

 the parenchyme of the leaves of other orchids. The placentae are coated 

 with delicate, thin- walled cells. 



Chemical Composition — Vanilla owes the fragrance for which it 

 is remarkable to Vanillin, which is found in a crystalline state in the 

 interior or on the surface of the fruit, or dissolved in the viscid oily 



^ This juice like that of the squill has an statement (first made by Berg) from the 



irritating eflfect on the skin, a fact of which examination of very aromatic pods produced 



the cultivators in Mauritius are well aware. in 1871 at HiUfield House, Eeigate. We 



^ Vanilla grown ia Europe is devoid of have even failed in finding tliose cells in 



such cells. We can fully corroborate thi» any vanilla of recent importation (1878). 



