136 THE AUSTRALIAN NATURALIST. 
AERATING ROOTS OR PNEUMATOPHORES OF 
MANGROVES (AVICENNIA). 
By Miss Acnes A. BREWSTER. 
‘These are curiously modified roots, whose duty is to stand 
erect and take in an air supply to the ordinary roots of the 
Mangrove. They are joined to the normal roots by a stalk- 
like constriction. The lower part of an aerating root, which is 
sunken in the mud, is darker in colour than the upper, more 
exposed, portion, which projects above the water at low tide. 
On breaking it across in the lower part, it is seen to consist of: 
(A) A central woody zone enclosing a small pith, and 
(B) An outer spongy soft area which carries an aerating 
system of intercellular spaces, called aerenchyma. 
These air spaces are continued into the upper part of the 
aerating root, and lead into little round lenticel-like patches 
dotted over the outer surface of the erect root. | When ex- 
amined with a lens these “doorways” or openings for the in- 
gress of air are seen to consist of an outer circular rim of bark 
having the centre filled with loose corky cells with spaces be- 
tween to allow of the passage of air. 
Another interesting feature is the presence of fibrous hori- 
zontal mooring roots.on the lower parts of the pneumatophores, 
confined chiefly to the landward side, and having. small fibres 
which penetrate the mud, thus anchoring the aerating roots and 
giving them more power to resist the pull of the outgoing tide. 
OBSERVATIONS ON THE LEAR-CUTTING BEE, 
MEGACHILE CHRYSOPYGA, 
By Miss Maset N. Brewster. 
We made some very interesting observations at Clarence 
Siding, Blue Mountains, in January, 1919. At the end of a 
long stone verandah were a number of rose bushes, two clumps 
of honeysuckle, and nearby were apple, plum, hazel-nut, and 
quince trees. There were numbers of the dark leaf-cutting 
bees busily working all day among the leaves of all these trees 
till 7 o’clock at night. 
Some of the smaller branches of the rose bushes had their 
leaves reduced to shreds by the too-frequent visits of these 
workers. We watched them approach the bushes, and they 
