105 
Nov., 1924 The Queensland Naturalist. 
EVP]XJXG MEETTXCr, 2()th 0(’T0BEK, 1924.— Pro- 
fessor E. J. Goddard presided, and there was a ^ood at- 
tendance of members and visitors. Mr. AV. D. Francis 
(Assistant Government Botanist) delivered a lecturette 
on ‘^Buttressed Trees of the Queensland Rain-forests.^’ 
The origin of plank buttresses in rain-forest trees 
had recently been the subject of investi«'ation by the 
lecturer, and the deductions he had drawn were con- 
tained in a paper recently prii}ted in the “ Proceedin^-s 
of the Royal Society of Queensland.” In rain-forests 
the absence of much direct sunlight on the soil surface 
and the fertility of the humus, containing upper layers 
of the soil, both tend to develop the surface roots. Owing 
to the high humus content of the surface soil and its 
avidity for oxygen, oxygenation of the sub-soil is re- 
tarded, and this acts still further towards the develop- 
ment of an extensive surface root system. The lecturer 
contended it would appear that in those cases where 
buttresses have been evolved the upper parts of the prin- 
cipal surface roots have acquired an aerial character, and 
are subjected to .some of the conditions operating in 
stems. The ])erpendicular elongation of the stems is a 
very profmiinent characteristic of the trees of tropical 
and sub-tropical rain forests, and is attributed to the 
attractive agency of ligtht, acting in conjunction with 
the normal upward growth in opposition to gravity. The 
upper parts of the principal surface roots in buttressed 
species may be affected by the same conditions, and in 
this way the perpendictilar extension which constitutes 
buttresses may arise. The adaptation of roots to an aerial 
environment is facilitated by the high relative humidity 
of the air and the exclusion of a* great amount of direct 
sunlight in rain forests. These two conditions there- 
fore are probably factors of considerable importance in 
the production of buttresses. 
Alessrs. Geissmann, (’urtis, Young, AA^hite, Dr. E. 0. 
Marks, and the President discussed the address. 
Airs. C. A. Alessmer exhibited several orchids from 
the Xational Park, ATacpherson Range, and a flowering 
spray of dlelmholtzia glaberrima, a most beautifuj: native 
flowering i)Iant of flag-like growth, found along the 
watercoures of the higher parts of the Alaepherson Range. 
Air. J. E. A'oung exhibited a pot of Sarcochilus Ilart- 
manni, in full flower. The plants Avere obtained in the 
Xational Park, Alaepherson Range, and rex)resented a 
