214 Sargant and Arber .— The Comparative Morphology of 
orientation is different. For in Elettaria the bundle P' travelled through 
an angular distance of about 90° in the sheath before running into the stele. 
Taking the insertion of the stalk on the sheath as a fixed point, and making 
the diameter of the section which passes through it vertical, the cotyledonary 
traces P and P' in VIII lie on the horizontal diameter. But in Roscoea 
the trace P' runs straight into the stele from the stalk, and P travels round 
to the opposite extremity of the vertical diameter before entering the stele. 
In the two other Roscoea seedlings there is no lower sheath at all, which 
leads to greater modification in the vascular skeleton. The insertion of the 
upper sheath coincides with level IV, and the section of P f which appears in 
Text-fig. 33. Roscoea purpurea , Sm. Diagram of first node in two other seedlings. 
the sheath is already running into the stele of the axis (Text-fig. 33). 
Root-plates are formed early, to correspond with the great development 
of cauline roots at the node (r } r, r, r). In one seedling the plates are 
found above the node; in the other they begin just below it. Between 
root-insertions the root-plates sometimes break up. Sections can be found 
which suggest the symmetrical arrangement of VII in the Elettaria 
diagrams. 
Though we have used Diagrams VII and VIII from Elettaria to 
explain the structure of Roscoea , there is one great difference between the 
two genera. In all three Roscoea seedlings the central group of protoxylem 
is absent. Each root-plate and each cotyledonary trace retains its own 
protoxylem, which is more or less definitely internal to the other elements. 
Alpinia calcarata^ Rose. We have made preparations from four 
seedlings, and drawings of five. They are small compared with those of 
Elettaria. The cotyledonary sheath is short, and the plumule very soon 
