472 THE POPULAR SCIENCE MONTHLY. 



well known to be chiefly salicylate of methyl, readily prepared from 

 salicylic acid and wood-alcohol ; and the oil or essence of pineapple 

 is precisely butyric ether, manufactured largely from waste materials. 

 Acetate of amyl and valerate of amyl are supposed to represent the 

 flavor of the apple and the pear, but how accurately they coincide 

 with the actual flavor-substances of these fruits has not been demon- 

 strated. Formate of ethyl, another compound ether, is used in so- 

 called peach-essence. Numerous fruit-flavors, used for culinary ex- 

 tracts and largely for soda-fountain sirups, are manufactured as 

 mixtures of ethers, by recipes varying with different manufacturers. 

 Many of these, resting on no due authority, are unwholesome mixt- 

 ures, often spurious imitations of the true fruit-flavors, and again 

 hurtful by reason of excessive proportions. As to the chemistry of 

 the production of flavoring ethers in plants, some guesses were pre- 

 sented under the head of sugar fermentation. 



5. Alkaloids. Substances strongly affecting the nervous system, 

 as medicines or poisons, of course do not occur in the edible fruits, 

 and we are not in the habit of placing potent compounds among the 

 constituents of fruits as a class; nevertheless, when we think of it, no 

 small proportion of the banes and antidotes of the vegetable kingdom 

 is matured in seeds and their coverings. In the poppy-fruit, the cap- 

 sule or pericarp furnishes at least sixteen distinct alkaloids, including 

 morphine, while the seeds are harmless, and yield an oil much used 

 for food. In the fruit of the nux-vomica, the seeds are deadly with 

 strychnine and other poisonous alkaloids, while the juicy pulp is but 

 very slightly impregnated with these bitter poisons (Fluckiger and 

 Hanbury, "Pharmacographia," p. 384). The seeds of henbane, and 

 stramonium, and the Calabar-bean, contain potent alkaloids. The 

 unripe tomato often contains traces of solanine, a poisonous alkaloid, 

 which disappears during ripening, probably by a glucosic fermenta- 

 tion. Tlie same alkaloid is sometimes found in the green or exposed 

 parts of potato-tubers. 



Many of the vegetable alkaloids are stable compounds, having 

 clearly-marked chemical characteristics. Some of the opium-alkaloids 

 closely resemble others in their composition. Different species of the 

 same family often yield the same alkaloids. The theobromine of the 

 chocolate-nut can be changed bv the chemist into caffeine, the alka- 

 loid of the coffee-berry. Such an insight has been obtained of the 

 structure of conine, the alkaloid of the classic poison hemlock, that it 

 has been formed from inorganic materials, through the processes of 

 the laboratory. But no evidence has been obtained as to the steps 

 through which alkaloids are formed in the living plants. 



It is little enough we know of the productive chemistry of plants. 

 As, at the beginning, we had need to plead ignorance of plant-con- 

 stituents, still more, at the end of our brief survey, must we declare 

 ignorance of the chemical genesis of those constituents. We can 



