78 STUDIES ON APPLES. 
Mangin“” 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 
issmall. 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 yellow 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 necessary in this connection. 
Much of the material found in Mangin’s review is also found in an 
article by Reynolds Green,’ 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; 1898, 7: 37, 121, 325. 
Science Progress, 1896, 6: 344. 
