346 LECTURE XXI. 



a restitution into proteid having previously taken place, and non-nitrogenous sub' 

 stance (in the first place probably glucose) being made use of in the process. 



This significance of asparagin was clearly perceived by Theodore Hartig, 

 so long ago as 1858, as is seen from his statement as follows : 'This apparently 

 general occurrence of this crystallisable substance in all the young cell-tissues, 

 indicates that its solution is the form in which the nitrogenous nutritive substance 

 of plants, formed from the reserve-materials, is moved from cell to cell.' The fact 

 that Hartig's important discovery remained so long in abeyance, is to be ascribed 

 to the circumstance that this able investigator here, as in many other cases, employed 

 a very peculiar and often unintelligible nomenclature, and termed asparagin ' Gleis.' 

 Our knowledge of this body was only carried further in 1872, by an investigation of 

 Pfeffer's ; he proved that the accumulation of asparagin during germination in the 

 dark, is due to the fact that in this case there are not suflficient carbo-hydrates present 

 to afford the material for the construction of proteids out of asparagin. If seedling 

 shoots grown in the dark and abounding in asparagin are exposed to strong light, 

 and a fresh supply of carbo-hydrates produced by assimilation, the asparagin dis- 

 appears, and proteid substances are formed at the same time. 



Moreover, in the formation of asparagin, the end appears to be not simply the 

 rendering the nitrogenous substance transportable. The fact, discovered and insisted 

 upon by Borodin, that asparagin arises even in cut-ofF buds and older shoots 

 which are allowed to grow, and therefore in the cells which are then beginning 

 to grow, proves that in the formation of asparagin it is not simply a matter of 

 conveying proteid-forming substance into the young organs, but that here, as in the 

 formation of peptone and in the inversion of cane-sugar and inulin, we may assume 

 that it is a matter of giving the plastic substance a form in which it is directly suited 

 for the nutrition. of growing protoplasm; or, as I expressed it in the beginning, to 

 convert the passive form of the reserve-material into an active one. 



The universal occurrence of asparagin asserted by Hartig, but disputed later 

 by Pfeffer, was again established by Borodin in 1878 in a detailed treatise, going 

 more exacdy into the conditions under which asparagin is to be detected. 

 Under normal conditions of vegetation during vigorous growth, and especially 

 under the influence of intense light, the asparagin is usually employed, according to 

 Borodin, for the formation of proteid, and for growth, as quickly as it is itself pro- 

 duced — an amount sulBciently large for detection only rarely occurs during normal 

 vegetation. Hence, to demonstrate the presence of asparagin in growing parts, ab- 

 normal conditions must be induced ; either by allowing the plants to grow in the dark 

 or in a feeble light, or, better, by placing branches in water, and employing the same 

 methods as before. The surest method, according to Borodin, is to make single 

 buds or the young apices of shoots grow in the dark, or in a feeble light; for by 

 this means, in part, the addition of carbo-hydrates from older parts, or even from 

 reservoirs of reserve-materials, is prevented, and in part the new formation of carbo- 

 hydrates by assimilation is excluded, and thus the reconstruction of asparagin into 

 proteid made impossible. Asparagin is therefore accumulated under the conditions 

 named, and can be demonstrated in sections under the microscope by the addition 

 of alcohol, in which it crystallises in a characteristic manner. In this way Borodin 

 succeeded in effecting the accumulation of asparagin, and in demonstrating its 



