BY C. T. MUSSON AND W. M. CAUNK. 663 



reddish, like the unexposed bark-layers; the terminal cells are 

 loosely compacted and free fiom any protective covering. On 

 stripping away the stem-bark down to near the wood, the course 

 of these growths is readily traced to both terminals. Within 

 the lower layers of bark, there is a rapid accumulation of waterj^ 

 liquid which forms blister-like swellings In seeking a cause for 

 these exceptional growths, we need to consider the conditions 

 under which the trees live. Usually found near watercourses or 

 in swamps, these trees are seldom found away from such locations 

 as allow of their becoming surrounded by water after heavy rain, 

 with the consequent filling of creeks and waterholes. The trees 

 may stand for months actually in water; whilst, on the water 

 disappearing, their location may dry out, leaving them to battle 

 through periods of drought. They have, therefore, to contend 

 with two very opposite sets of conditions as regards water-supply, 

 shortage, even to almost complete absence; and, at the other ex- 

 treme, actual flooding which may endure for months. It is 

 worthy of note that these conditions operate with respect to cer- 

 tain Eucalypts, Casuarinas, and other species of Melaleuca; ad- 

 ventitious roots have, however, only so far been seen on the tree 

 under notice. It would be interesting to know the actual root- 

 conditions especially with regard to root-hairs, as to quantity and 

 variability in number during the extremes referred to; also 

 whether any symbiotic organisms exist thereon; and if so whether 

 there is any correlation between their presence and the conditions 

 of habitat. Fungus mycele is commonly found here on roots of 

 many and diverse plants; its presence may have a special signifi- 

 cance in relation to our soil and climatic conditions. With 

 respect to the part played by these adventitious roots in the life 

 of the tree, several suppositions present themselves. They may 

 function as aerating organs, though the extremities are never 

 exposed directly to the air, being always hidden beneath the 

 bark layers. The stilt-roots of the Mangrove are probably not 

 analogous.* 



**' BespiratioD in the roots of Shore-plants," Dr. J. Bancroft, Report Aust. 

 Assocn. Adv. Science, Sydney, 1887, vol.i. p. 327. 



