58 Bunting—The Structure of the Cork Tissues in 
In the cork region of Acena reptans very minute inter- 
cellular spaces are present ; the elongated quadrangular cells 
are arranged in multiseriate layers of large and small cells, 
the former situated toward the exterior margin, the latter 
toward the centre of the section. The roots studied were 
young, and had only two multiseriate layers, each contain- 
ing four rows of cells. The annular arrangement is also 
noticeable from the fact that the inner multiseriate layer is 
composed of cells whose walls are devoid of pigment, while 
the outer layer is composed of cells whose walls contain 
pigment. 
Group Rube@.—In Rubus occidentalis and R. villosus very 
minute rectangular intercellular spaces are present, but they 
are not arranged with the regularity that is characteristic of 
the genera of the foregoing groups. Pigment is present in 
the contents of the outer sloughing-off layers, although in the 
sections which I studied the flattened uniseriate layers with 
pigment were not found. When stained with aniline green 
these layers appeared to be differentiated, the contents of a 
uniseriate layer being stained more deeply than those of the 
multiseriate layers. 
Group Rose@.—I\n the only species of rose examined, the 
cork was composed of flattened quadrangular cells ; the whole 
region consisting of alternating layers of cells with and with- 
out pigment contents. The interior and exterior tangential 
walls of the non-pigmented layers are curved outwards, so 
that the pigmented layers have their cells compressed. The 
intercellular spaces are minute and are arranged irregularly as 
in the Group Rudeg. 
Group Prunee.—\n Prunus virginiana the cork cells are 
flattened and tabular in shape. They are uninterruptedly 
connected with each other, so that there is no trace of inter- 
cellular spaces. The layers of cells are all uniform in appear- 
ance, and thus division into annular rings, which has formed 
so conspicuous a feature of the preceding types, is not observed. 
