BY JAMES M. PETRIE. 827 



nitrogen is increasing rapidly with development. Here Schulze 

 found different amino-acids appearing at particular periods. 

 During the first six days leucin, tyrosin and the hexone bases 

 were present; and, on about the sixth day, the relative proportions 

 of these was the same as that obtained by acid-hydrolysis. But 

 gradually these decreased till, in the two or three weeks' seedlings, 

 tyrosin had disappeared entirely, leucin and arginin were only 

 found in traces, and often none at all. Their place was now 

 taken by other amino-acids(90) such as phenylalanin, amino- 

 valerianic acid, a-prolin, iso-leucin, and tryptophane. 



Different plant-species produce different amino-acids ; and 

 again, even in the same species, these vary according to whether 

 the plant has developed in light or in the dark. Therefore it is 

 apparent that the protein-molecule in the various plant-species 

 does not decompose in the same way, and even in the same 

 species is this true. Most of the known hydrolytic products of 

 protein have been isolated at various stages of germination. 



The fact that considerable quantities of amino-acids exist in 

 the early stages of growth, and that these gradually disappear to 

 a small remainder, is explained by Schulze's experiments. (91) He 

 says that th°se primary decomposition-products are further 

 broken down, yielding a nitrogen-containing residue (perhaps 

 ammonia) which is used up for the synthesis of asparagin and 

 glutamin. 



We may now reuumerate the different compounds which have 

 been found in germinating seedlings. (1) The proteins and their 

 cleavage-products, viz., proteoses, polypeptides, amino-acids, and 

 ammonia. The mono-amino-acids — leucin, iso-leucin, tyrosin, 

 phenylalanin, valin, prolin, and tryptophane; the diamino-acids — 

 histidin, arginin, lysin; the amides — asparagin and glutamin. 

 Besides these we find the hydrolytic products of the other seed- 

 constituents. (2) From nucleo-proteins the purin bases are split 

 off by the nuclease enzyme; other enzymes then remove the (NH 2 ) 

 group from the amino-purins, and adenin passes into hypo- 

 xanthin, guanin into xanthin, and by decomposition of these we 

 get guanidin and allantoin. (3) From the phosphatides, chiefly 



