830 THE ROLE OF NITROGEN, ETC., I., 



accumulation of asparagin in etiolated seedlings was first proved 

 by Pasteur, in 1851; and Pfeffer, in 1871, proved that the cause 

 of this accumulation was the lack of sufficient carbohydrate. The 

 amide, glutamin, on the other hand, Schulze(99) first separated, in 

 1895, from the beet. 



The second stage in the synthesis is shown by the disappear- 

 ance of the accumulated amides when the plant is grown in the 

 sunlight, and the simultaneous formation of protein, as if certain 

 of the products of carbon-assimilation were necessary. All 

 evidence points to the latter being carbohydrates, since, if these 

 be supplied, the protein-formation proceeds in the dark. Brown 

 and Morris(lOO) have shown that all foliage leaves contain diastase 

 in varying quantities, and that leguminous leaves have an 

 enormous diastatic activity; Pisum sativum, for example, con- 

 tained sufficient of the enzyme to convert 24 times its own dry 

 weight of starch into sugar in two days, while most of the non- 

 leguminous plants had a value less than 1. It is significant that 

 we have here an unfailing source of sugar in the particular plants 

 which contain the largest amount of nitrogen-compounds on the 

 upward grade. 



The following table shows the distribution of amides in the 

 seedlings of Lupinus albusWL) : — 



Leaves stalks cotyledons roots 



6-6% 21-1% 17-6% 10-2% of amides 



in the dry material, while the etiolated leaves of the same con- 

 tained more than 17 %. The effect of carbon-assimilation is 

 evident in the green leaves; asparagin disappears and protein is 

 formed. 



Now these facts are but a few isolated milestones on the 

 upward track, with very long intervals between. We cannot 

 see clearly why amides should suffice and amino-acids be insuffi- 

 cient in the synthetic processes. Is it that asparagin and 

 glutamin form a halting stage, or common centre, upon which 

 act both disintegrating and upbuilding forces, that many inter- 

 mediate stages are quickly run through, that these are of infinitely 

 labile compounds changing constantl} 7 , melting away into some- 

 thing else when we try to follow them with our imperfect methods, 



