20 ESSENTIALS OF BOTANY 



25. Chemical Tests for Proteids. — All proteids (and very 

 few other substances) are turned yellow by nitric acid, and 

 this yellow color becomes deeper or even orange when the 

 yellowish substance is moistened with ammonia. They 

 are also turned yellow by iodine solution. 



EXPERIMENT VH 



Detection of Proteids in Seeds. — Extract the germs from some 

 soaked kernels of corn and bruise them ; soak some wheat-germ meal 

 for a few hours in warm water, or wash the starch out of wheat-flour 

 dough ; reserving the latter for use, place it in a white saucer or por- 

 celain evaporating dish and moisten well with nitric acid ; examine 

 after fifteen minutes. 



26. The Brazil-Nut as a Typical Oily Seed. — Not many 

 familiar seeds are as oily as the Brazil-nut. Its large size 

 makes it convenient for examination, and the fact that this 

 nut is good for human food makes it the more interesting 

 to investigate the kinds of plant-food which it contains. 



experi:ment viii 



Testing Brazil-Nuts for Plant -Foods. — Crack fifteen or twenty 

 Brazil-nuts, peel off the brown coating from the kernel of each, and 

 then grind the kernels to a pulp in a mortar. Shake up this pulp 

 with ether, pour upon a paper filter, and wash with ether until the 

 washings when evaporated are nearly free from oil. The funnel 

 containing the filter should be kept covered as much as possible 

 until the washing is finished. Evaporate the filtrate to procure the 

 oil, which may afterwards be kept in a glass-stoppered bottle. Dry 

 the powder which remains on the filter and keep it in a wide- 

 mouthed bottle. Test portions of this powder for proteids and for 

 starch. Explain the results obtained. 



