7o STUDIES ON APPLES. 



Mangin rt contributed a comprehensive review, referred to at the 

 beginning of this paper, and studies which appear to be worth cor- 

 roborating at least by the microchemist, and if proved to be reliable, 

 they may be used in connection with chemical investigation. Mangin 

 considers that pectic compounds are constant constituents of cell 

 membranes; that pectose itself may be a mixture of several similar 

 compounds or a single body; that pectose seems to be elaborated 

 earlier than cellulose in young tissue, and forms the intermedullary 

 layer in mature tissue; that it is not elaborated from cellulose; and 

 that soft parenchymatous tissue is essentially characterized by a very 

 close association of cellulose and of pectins. 



Many coloring agents are stated to dye the pectins in plant tissues 

 and differentiate them from cellulose but not from nitrogenous matters 

 nor from lignin, suberin, or cutin, so that the number of suitable dyes 

 is small. These dyes are the safranines, methylene blue," bleu de nuit," 

 and naphthalene blue R in crystals. Safranine is said to color the 

 nitrogenous bodies and lignin a cerise red, while the pectins are colored 

 a } r ellow orange. Methylene and " bleu de nuit" color nitrogenous 

 bodies and lignin a beautiful blue, while the pectins are colored a 

 violet blue best seen by lamplight. A mixture of naphthalene blue R 

 in crystals and acid green J. E. E. E. (poirier) (equal parts of a 1 per 

 cent solution of each) colors pectins violet and other bodies green. 

 Ruthenium red is also recommended. 



The above review does not nearly do justice to Mangin's contribu- 

 tions. Since the methods used are distinctly microchemical, however, 

 a more extended notice does not seem necessar}^ in this connection. 

 Much of the material found in Mangin's review is also found in an 

 article by Reynolds Green, 6 who discusses the pectin bodies from the 

 botanist's point of view. 



Most of the facts, brought out in the above review are tabulated, for 

 convenience of reference, in Table VII (see p. 80). 



Compt. rend. 1888, 107: 144; 1889, 109: 579; 1890, 110: 295; 1893, 116: 653; 

 J. bot. 1891, 5: 400-440; 1892, 6: 12, 206, 235, 363; 1893, 7: 37, 121, 325. 

 & Science Progress, 1896, 6: 344. 



