Roots o/Terminalia Arjuna. 
1 55 
distinguished partly by the form of the cells, but more distinctly by 
their contents. The central core consists of large cells which are 
square in longitudinal section, while the others are elongated in 
the axial direction; intermediate stages however occur. The 
differentiation of contents is very sharp; the cells of the central 
core contain clear vacuolated protoplasm with prominent nuclei 
while the surrounding cells have small inconspicuous nuclei and are 
filled with a deeply-staining granular substance. No intercellular 
spaces occur between the cells of the root-cap. Root-caps of this 
form were found both in the horizontal and the vertical roots ; in 
neither case are root-hairs developed at all. 
Slight structural differences were noticed in roots collected 
from different environmental conditions: those growing wholly or 
partially submerged have the vascular tissues less developed, and 
do not form a periderm till a later period ; also the hypodermal 
layer is less distinct, especially in the vertical roots which are less 
branched or unbranched. In some roots from the edge of the river, 
which presumably had been dry for a longer period, the conjugating 
parenchyma is much less developed. 
Some seedlings were also examined; these did not show any 
trace of the peculiar roots, but since the seeds germinate and start 
life on the dry banks and not in the river-bed, this is not so 
remarkable. In general structure the roots of these seedlings are 
very like those described, but without the great cortical lacunar 
system. 
The roots of Terminalia differ markedly from the pneumato- 
phores of Sonneratia, 1 in not possessing the striking peripheral layer 
of cork with lenticels characteristic of the latter genus. Even old 
roots of Terminalia which had cast off the primary cortex had no 
lenticels. The hypodermal layer of cells in Terminalia is not 
connected with a cambial layer, and no openings communicating 
with the outside air occur in it. Another point in which roots of 
Terminalia Arjuna differ from typical pneumatophores is the complete 
absence of stem characters, such as pith, etc.; as far as vascular 
anatomy goes they are perfectly normal roots. Though these roots 
seem to be for purposes of aeration, they cannot be described as 
as true pneumatophores, in Westermaier’s sense. 3 
Mr. Burkill suggested from observations made while collecting 
the material that the aerating roots of Terminalia are probably 
1 Goebel. Ber. Deut. Bot. Ges., 1886. 
* WesternifUer. Loc. cit., 1900. 
