New YorkK AGRICULTURAL EXPERIMENT STATION. 179 
inner lamella, distinctly stratified in structure, at least in the 
heavier parts at the angles. 
This conception involves the idea of the passage in the grow- 
ing walls of the pectose substances by gradual filtration 
through the cellulose Jayers from the protoplast where they 
originate toward the exterior, and is at the same time in ac- 
cord with the idea of Allen (1902: 31) that the young cambium 
wall really forms the basis of the middle lamella of the older 
tissues. 
THE ACTION OF THE ENZYM ON THE CELL-WALL. 
The rapidity of the invasion of vegetable tissues by the car- 
rot rot organism was discussed in our earlier report (1900 :307— 
312). As there explained it rots only parenchymatous tissues. 
The invaded tissues become watery and usually more or less 
darkened in color when exposed to the air. The cells rapidly 
lose all coherence and always show a sharply defined line of 
demarkation, indicating that the softening occurs quickly and 
completely after it begins. Examination of such recently de- 
composed tissues under the microscope shows the cells to be 
already isolated or easily separable along the plane of the 
middle lamella. The protoplasmic sac within the cell is col- 
lapsed, more coarsely granulated than normally, and evidently 
dead and in the process of disorganization. Bacteria teem 
around and between these cells but are so rarely seen within 
them that where this does occasionally occur, one is led to 
attribute it to mechanical rupture of the softened walls rather 
than to direct solution. (See figures 1, 5 and 6.) 
In the case of the inoculation of a cut surface of root kept 
in ordinarily dry atmosphere, the invaded area dries out very 
rapidly; if, however, it is kept in a saturated atmosphere gray 
drops of exudate teeming with bacteria form on the surface 
and the tissues underneath become sunken. It is evident, 
therefore, that among the products of the bacterial growth are 
active osmotic substances which draw the water, and of course 
soluble nutritive matters, from the dying or dead protoplasts. 
The organism is powerless to invade wilting or pithy and par- 
tially dried-out vegetable tissues of even the most susceptible 
