664 THE ADVENTrXIOUi ROOTS OF MELALEUCA LliS AHll FOLIA, 



These Tea-tree adventitious roots can hardly be air-passages, 

 fof they arise, as do true roots, not in the bark, but from beneath 

 the cambium; therefore, connecting with the tissues in use for con- 

 veyance of sap upwards. Their place of origin and the peculiar 

 situation of their terminations seem to indicate that they are in 

 some way connected with the tree's water-supply; possibly they 

 are a means for reinforcing it at certain times from the stores in 

 the lower layers of bark. Our observations have been made 

 during the last few years, which have been noticeably dry; the 

 outgrowths appear as dry as the outer bark; though, as stated, 

 there is a plentiful supply of moisture deep down in the bark. 

 The trees havp suffered much through the continuous dry sea- 

 sons; and are very bare of leaves; apparently a flooded period is 

 required to restore them thoroughly to full vigour. 



A third possible explanation suggests that these outgrowths 

 may be of no special present use, but have been so in the past; 

 that they are vestigial organs. It lias been stated that " adventi- 

 tious roots occur in places where the atmosphere is warm, stag- 

 nant, and loaded with moisture:" these conditions would be 

 present for considerable periods when these trees stand in water, 

 as we have seen to be the case for months together. The fact 

 that such root-growths seek the dark recesses of the bark is quite 

 natural, if they are really absorbing organs approximating in 

 function to true roots; though in this case their action will be 

 like that of hairless roots in water, absorption taking place 

 through the loose unprotected cells at their extremities. 



These roots should also be compared with those of the Moreton 

 Bay and other fig-trees; tho.se of the latter striking directly into 

 the air, and remaining there. Taking all the circumstances into 

 consideration, it is believed that these adventitious roots are of 

 assistance in the general upward sap-circulation, peiforming 

 auxiliary duties at some sjjecial time, most likely during one of 

 some particular stress. This may be when the soil-roots are 

 completely immersed in water, and are perhaps unable to function 

 properly; at such times it is possible that these roots take up the 



