58 MISSOURI BOTANICAL GARDEN. 
by practically all botanists as being present in fungi we can 
hardly come to but one conclusion regarding the existence 
of a delignifying enzyme. 
EXPLANATION OF PLATES. 
Plate 1.— 1, Portion of transverse section of wood of Populus tremu- 
loides showing several wood fibers with a third, inner, cellulose layer. 
This layer is colorless, as the section is stained with phloroglucin which 
is a test for lignin. This supernumerary layer is characteristic of the 
species of the genus Populus so far as they have yet been examined, five 
of the endemic North American species from the various parts of the 
country having been tested. 2, Portionof a transverse section of wood of 
Pinus palustris showing one annual ring of growth. The thicker walled 
cells form the summer wood of the ring, while the thin walled ones make 
up the spring wood. This section has been boiled until the lignin was 
extracted from the spring wood, and was then stained with phloroglucin, 
atest forlignin. The red walls have reacted with the chemical show- 
ing that lignin is still present in the summer fibers. The yellow cells 
have retained their normal color to a greater or less extent and gave no 
reaction with the phloroglucin, thus showing that they have been de- 
lignified quite completely. The section shows the relative solubility of 
the lignin in the two parts of the annual ring. 
Plate 2.—1, Portion of a transverse section of wood of Picea rubens 
boiled for 27 hours. This has been stained with chlor-iodide of zinc, 
a test for cellulose. The cellulose has been colored blue while the other 
parts of the walls are of their normal color. This shows the delignify- 
ing action of boiling water upon the lignin of the fibers. 2, Transverse 
section of wood of Populus balsamifera cut from a freshly felled tree and 
stained with chlor-iodide of zinc. The thick supernumerary layer of 
cellulose is colored blue. 38, Transverse section of wood of Sassafras 
Sassafras boiled 20 hours and stained with chlor-iodide of zinc. This 
is drawn with a smaller magnification than are the other figures. It 
shows the frequency of the cellulose layer, in the fibers of the wood. 
’ Note that there is no cellulose present in the last cells formed in the ring, 
which arein a vertical line near the left of the figure. 4, Transverse 
section of wood of Sassafras Sassafras drawn on the same scale as the 
_ other figures. This was boiled and treated with chlor-iodide of zinc 
‘and shows the character of the delignified layer in the fibers. Most 
of the fibers adjacent to the vessels and tracheids do not have the 
cellulose layer. 
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