76 THE AUSTRALIAN NATURALIST. 
came up and pulled it over, still wrong side up, just as the first 
spider had done, but after a few knocks and pushings from in- 
side to settle it in position, the door was completely turned over 
and was now in its normal position. ‘The same experiment was 
repeated a few minutes later with exactly the same result. 
MUCILAGE CELLS AND RAPHIDES OF HIBBERTIA. 
By A. A. Brewster, F.T.C. 
The genus Hibbertia belongs to the family Dilleniaceae, and 
is a typical xerophyte. In most species the leaves are small, and 
in the beach growing H. volubilis the leaves are larger, but with 
upper bright surface, and the lower clothed with hairs. As the 
name denotes, it is a twining plant. A marked feature of all 
parts of the internal structure of the Hibbertias is the presence 
of erystals of oxalate of lime, called raphides, which are needle 
shaped and usually occur in bundles like faggots. The beauti- 
ful yellow petals are worth studying. First. there are the 
curious deeply lobed cells, giving an increased surface of the 
protoplasm and hence more working power. ‘Then there are the 
chromoplasts or yellow grains of protoplasm which give the 
colour to the petals. Finally there are curious elongate. sac- 
shaped mucilage cells which are capable of absorbing and _ stor- 
ing relatively large quantities of water. Within these sacs are 
bundles of raphides which are secreted to get rid of the in- 
jurious oxalic acid—a waste metabolic product—by fixing it with 
calcium and so rendering it innocuous. 
EXCURSIONS TO PENNANT HILLS. 
May 6th. On arriving at Pennant Hills we were at once 
struck with the ecological aspect—the contrast of the growth— 
on the shale area (Wianamatta shale) where the land yielded tall 
eucalyptus trees and shrubs.. Further on we got on to sandy 
patches where Banksias, Hakea, ete., flourished. The leaders 
pointed out various interesting types as we passed down the 
creek—which is on the west side of the railway line, about a 
mile from the station, turning to the right at the far end of 
Stephens Street. The entomologists, with Mr. Gallard, found 
ample material in the creek pools. Mr. Steel had on view liv- 
