VANILLA. 157 
grecum fragrans, Capparis spinosa, Cereus grandiflora, and Ces- 
trum vespertinum, but in an inferior degree, also strongly in the 
flowers of Azara microphylla*. 
In the green state the pod consists of an acid pulp containing 
raphides in needles, and crystals of oxalate of lime (these bodies 
being also found in the stalk and leaves); the pods also contain 
a citron-coloured oil surrounding the seeds. When this oil is iso- 
lated by ether, it is found to possess an odour somewhat similar to 
that which the bean will furnish at maturity. As maturity pro- 
gresses, the lower end of the pod begins to turn yellow and dis- 
engage a characteristic penetrating odour recalling that of bitter 
almonds; the valves of the pod crack open and permit the escape 
of a small quantity of a balsamic oil. By degrees the colour 
darkens, the epidermis softens, and the true odour of vanilla begins 
to develop. This natural fermentation gradually progressing up 
the pod, the proportion of balsamic oil increases and exudes in 
thick reddish drops, especially if the split pod has been tied together 
at the end. ‘This oil is known by the name of Balsam of Vanilla, 
and in Peru it is very carefully collected by the planters, but not 
sent to Europe. The ripening process, thus slowly progressing 
upwards, does not reach the top or stalk part until about a month. 
The chemical changes which have meanwhile taken place inside 
the pod, through the combined action of the air and the sun, 
remains a secret process guarded by Nature. 
Some chemists are of opinion that the odorous principle is loca- 
lized in the centre of the fruit, in proximity to the seeds and the 
placenta, but others think that the entire fruit is concerned in its 
formation, as it undergoes such great changes. 
The artificial methods of hastening the maturity, either by hot 
water or by the exposure to sun-heat or stove-heat, have for object 
the production of a uniform ripening of the pod over its entire 
length all at once, and not by degrees up the pod as happens in 
nature. The artificial processes also prevent the splitting of the 
pod and consequent loss of perfume which occurs when the pod is 
left on the vine, 
The yivre or crystals which form on good vanilla were formerly 
thought to be benzoic acid, but the researches of Gobley disclosed 
the fact that they are quite a different body, which he termed 
Vanillin. The conditions favourable for its formation are: pre- 
—*® Described by Dean Hole, in his ‘A Book about the Garden,’ p. 234, as a 
hardy shrub. 
