CELL-CONTENTS AND FORMS OF CELLS. 167 



lated alkaloids in opium, probably contain the Phenanthrene 

 nucleus (C 14 H 10 ). 



PURINE GROUP. Caffeine, the characteristic alkaloid of 

 coffee, tea, and guarana, as well as theobromine associated with 

 caffeine in cacao and kolanut, are derivatives of Purine (C 5 H 4 N). 



AMINO-ACID GROUP. Asparagine, or the monamide of aspartic 

 acid, is very widely distributed throughout the plant kingdom. 



Consult J. W. Bruhl, " Die Pflanzen-Alkaloide " ; A. Pictet, 

 " The Vegetable Alkaloids," translation by H. C. Biddle ; O. A. 

 Oesterle, " Grundriss der Pharmakochemie." 



ASPARAGINE (C 4 H 8 N 2 + H 2 O) (/?-asparagine, the monamide of 

 aspartic acid) is an amido compound which is most widely distrib- 

 uted throughout the vegetable kingdom. It is found not only in 

 reserve organs as the tubers of the potato and dahlia, the roots 

 of althaea, belladonna, etc., and the seeds of the chestnut tree, 

 but it also occurs in young shoots as of asparagus and in peas, 

 beans, and other members of the Leguminosae. Asparagine has 

 also been detected in some of the fungi as the Agaricineae and cer- 

 tain of the Myxomycetes. Unlike certain derivatives of urea, it is 

 a plastic product playing a very important role in plant metabolism. 

 On account of its crystalline character and solubility in water, 

 it is classed among the translocatory substances, appearing not 

 only when proteins are being utilized by the plant, but when 

 they are being formed. The crystals of asparagine are formed 

 rather easily from the expressed juices of young shoots, and may 

 be obtained even in sections upon mounting them in glycerin. 

 The crystals vary in length from 0.3 mm. to 15 mm. (Fig. 98). 



Asparagine occurs in two forms, one of which is laevorotatory 

 and the other dextro-rotatory; the former is the one usually 

 present in plants. At 17.5 C., I part of asparagine is soluble 

 in 47 parts of distilled water; at 98 C., I part is soluble in 1.9 

 parts of distilled water. 



THE GLUCOSIDES or Glycosides are a class of plant substances 

 which under the influence of ferments split up into a number of 

 substances, one of which is always glucose (dextrose) or an analo- 

 gous compound. Van Rijn has proposed the class name Glykoside 

 for all substances of this group, restricting the name glucoside 

 to those which yield glucose on hydrolysis. The glucosides are 



