PRESENCE OF A TRUE MANNA ON A BLUE GRASS. 293 
swelling of the stem and base of the leaves which afterwards split 
or divide longitudinally as the substance increases in dimensions. 
It eventually enlarges to the size of a marble or the top of a 
man’s thumb. It is mostly white in colour and in general appear- 
ance resembles the corn-pop lollies of American confectionery, or 
the well known Eucalyptus manna. It is sweetish to the taste, 
is not moist, breaks down easily into fragments, and has a slight 
greasy feel. The surface is irregular, rugose, and granular. 
A vertical or horizontal section gives a kidney-shaped surface, 
showing a cavity opening from the stem and filled with the excre- 
ment of a microlepidopterous insect—(according to Mr. W. W. 
Froggatt, Government Entomologist, to whom it was submitted 
for an opinion). The substance is quite white throughout, and 
in section shows radiating lines to the outer surface. 
Microscopical Examination of the Manna.—When the powdered 
manna is placed upon a slide (better under a cover glass) and 
examined with the microscope, minute crystals are seen to be 
present in large quantities, With a quarter inch objective these 
are seen to be principally small prismatic crystals. They are too 
minute for the form to be determined, but under crossed nicols 
they polarize in faint colours of a light grey to dull yellow, and | 
extinguish parallel to the principal axis. It is to be supposed, 
therefore, that they are crystals belonging to the rhombic system. 
They are naturally crystallised mannite, It is perhaps worthy of 
note, that naturally crystallised mannite polarises faintly in 
colours, while the crystals formed artificially from the same 
material, do not polarise in colours, with the exception of light 
grey, although they change from light to dark on being revolved 
between crossed nicols, the greatest darkness being when the 
prisms are parallel to the crossed webs. This was found to be the 
case also in the natural crystals of mannite from the manna of the — 
sandalwood Myoporum platycarpum.’ 
aE OR OE Ee 
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2 Report on the vegetable exudations collected by the Elder Exploring 
Expedition.—Proc, R.S., 8.A., 1892. 
