156 Roots of Terminalia Arjuna. 
ephemeral, and functional during the wet season only. He considers 
it as probable that they die off when the rivers run dry. This 
suggestion appears quite plausible, since, when the soil is dry, the 
perennial horizontal roots would be in a medium where ordinary 
respiration is possible. This is a point that can only be settled by 
further observations of the plants in their native habitat. 
Summary. 
The vertical roots are for purposes of aeration as shown by 
the great development ol the lacunar system. 
The lacunas in the primary cortex are developed mainly from 
conjugating parenchyma. 
A secondary aerating cortex is produced in old roots in the 
region of the secondary phloem. 
No root-hairs are present, but a root-cap of a peculiar nature 
is formed. 
No direct connexion with the outside air was noted. 
These roots have none of the stem characters of typical 
Mangrove pneumatophores. 
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