12- THE UOLE OF NITROGEN IN PLANT-METABOLISM, iii., 



nitrogen. Even after this powerful treatment, the ammonia 

 distillation is drawn out for some hours, as is seen ni 

 Table xi., e. 



E. — The phosphotungstic precipitates, when dissolved, and 

 the reagent removed with barium hydroxide, begin rapidly 

 to decompose ; and, within a few days, considerable volumes 

 of trimethylamine are liberated. This strong evidence of 

 the presence of cholin is partly confirmed by subsequently 

 obtaining the characteristic haemin-like crystals of cholin 

 per-iodide, which are recognised under the microscope in 

 abundance. That this free cholin has not its origin in 

 lecithin or other lipoids occurring in the extract, is seen from 

 the small amount of lecithin, 05%, obtained by ether-extrac- 

 tion. Both cholin and betain have been identified by 

 Schulze in leguminous seeds. 



The same solution gives, with silver sulphate, a consider- 

 able precipitate containing xanthin-bases, and, after satura- 

 tion with baryta, a precipitate which probably contains 

 arginin. The total nitrogen- value of these basic compounds 

 is 20% of the non-protein nitrogen, but when the phospho- 

 tungstic precipitation follows hydrolysis, only 14% is ob- 

 tained. The difference is mostly accounted for by the forma- 

 tion of a large amount of melanoidin, which is explained by 

 Samuely* as probably due to the association of the nitro- 

 genous compounds with carbohydrates j^resent in the solution, 

 and their oxidation during the hydrolysis with acid. 

 Schmiedebergt noticed also that xanthin bases and carbohy- 

 drates gave rise to melanoidin, when boiled with acids. 



F. — In the examination of the solution for compounds 

 containing the amino-group, the following results wei'e 

 obtained : — - 



* Hofmeistei's Beittar;e, 1902. s.35.5. 

 t Arch. f. exp. Path. u. Phannak., 43, 1899, n.r,; 



