Roots of Cycas Seemanni , Al. Braun. 65 
thickness from about 15-33 mm. in the thickest por- 
tions. 
The roots investigated were the tap roots of the seedlings ; 
in the lateral roots no anomalous growth whatever was found. 
The abnormal thickening was confined to a region from 
30-40 mm. in length, measured from the junction of the 
stem with the root. 
In order to understand the phenomena which I am about 
to describe, it will be necessary first to give an account of 
the structure of the roots in question, before the abnormal 
development made its appearance. This was easily as- 
certained by making a series of sections from the younger 
portion of the root I found that the very young portions 
had usually the ordinary diarch arrangement of the bundles ; 
one case of a triarch root was observed. The primary 
structure need not be described in minute detail, as it agrees 
in the main with that recorded by Mettenius. The primary 
groups of the diarch xylem unite to form a median plate, the 
elements of which become to some extent separated from one 
another by the greater growth of the conjunctive parenchyma. 
The primary phloem-groups have the usual position on the 
right and left of the primary xylem-plate. The normal 
cambium arises along the inner side of these phloem-groups, 
and produces in the usual manner two masses of secondary 
xylem on the side towards the primary plate, while on the 
outside secondary phloem is produced. Except in one case, 
to be described later on, the normal cambial layer was not 
found to become continuous around the ends of the primary 
xylem. The pericambium was many layers of cells in 
thickness, as is usual in Gymnosperms, and it is owing to this 
fact that the abnormality to be presently described is possible. 
The pericambium is surrounded by a well-marked endodermis 
of the usual character. This is again surrounded by a wide 
cortex. The structure of the root at the stage which we are 
now considering may well be compared with the root of 
Taxus as figured by Strasburger 1 . It may here be mentioned 
1 Das botanische Practicum, p. 201. 
F 
