1908] HASSELBRING— ASSIMILATION OF PENICILLIUM 177 



certain atomic groups. According to Nageli, carbon is assimilated 

 from the groups =CH 2 and = CH, but in the latter case only when it 

 occurs in a chain of two or more C-atoms to which H is bound. Ben- 

 zoic acid is assimilated, but formic acid is not. On the other hand, 

 carbon is not assimilated when it is directly united only with O or N 

 but not with H. Accordingly, the CN group, oxalic acid, urea, and 

 similar substances, are not suitable sources of carbon. 



Subsequent researches showed that the conclusions of Nageli 

 were no longer tenable, since it was found that the molds were not 

 restricted to such specific groupings as he supposed. Reinke 6 

 greatly extended the list of substances which could be assimilated, 

 and showed that some of the particular groupings which Nageli 

 excepted could be utilized. Thus, for example, parabanic acid, 



/NH- CO 

 CO\ proved an efficient source of carbon for Penicillium. 



^NH— CO 



Diakonow 7 demonstrated that carbon from urea and from formic 

 acid could also be utilized by this fungus. 



All of these facts indicate that no general relation can at present 

 be established between the atomic structure of a substance and its 

 food value. The mechanism of assimilation probably differs with 

 each individual case and is as much dependent upon the nature of 

 the plant as upon the chemical reactions of the compounds used ; for, 

 as already stated, every substance that has nutritive value for one 

 plant will not serve as a food for all plants. 



It was with a view of gaining, if possible, some knowledge of the 

 complex problem of the chemistry of the assimilation of some of the 

 simpler compounds that the work reported here was undertaken. 

 It was thought that by studying the effect of a number of related com- 

 pounds on the growth of the mold fungi, and noting the variations 

 caused by different stimulating agents, it would be possible to gain 

 some knowledge of the probable chemical reactions by which nutrient 

 substances combine with the constituents of the living cell. 



This proved to be a most complex problem, whose solution is made 



6 Reinke, J., Unters. Bot. Lab. Gottingen. (Rev. in Bot. Zeit. 41:551. 1883, and 

 Just's Bot. Jahresb. 11:55. 1883.) 



7 Diakonow, N. W., Organische Substanz als Nahrsubstanz. Ber. Deutsch. 

 Bot. Gesells. 5:380-387. 1887. 



