February i, iSqs.] 
THP TROPICAL AORIOULTUmST. 
5«3 
native habitats gnma iiioro or less insoluiile, 
produce 11101*0 soluble products when grown in soiiio 
other coHUtrios. The ouestiou ia a wide one, and 
well worthy of being followed up, for it would be of 
the highest commercial importance if it could he 
nhown tliat free-yielders of inferior metarabic gum 
would in other soil and climate develop a tendency 
to the formation of arable gum (seo .1. dniUmta, 
/I. di'vnnri*^). 
Some notes by Dr. TIopff on an Australian Wat- 
tle glim aa compared with gum araliic will bo found 
in I’htinn. Jtunii., vii., 588. The experiments have no 
concliisivenoss, and tho source of tlie Wattle gum is 
not given, for it was probably unobtainable. 
I have divided the Wattle gums experimented 
upon into three provisional gi'oups. I could make 
sagacious guesses os to the groups into which many 
otlier Wattle gums are likely to fall, hut xirefer to 
confine myself to the record^ of facts. The classifi- 
cation of tho future will probably be into arabin and 
metavabin groups, in which case my groups IT. and 
III. will simply require to be united. The samples 
chosen for analysis were picked ones in all cases. 
Guovp I. (Aii.un.VN Ghoup.) 
jiroriit hoiiKiloitliijIhi, 
Acavia pfmfiJa. 
Acacia HcnUt. 
They are readily and entirely soluble in cold 
water, like Turkey gum arabic, for which they form 
an excellent substitute. Arabin is their cluu-acter- 
istio and main constituent. Following are analyses : — 
Arabin. Metarabin. Moisture. Ash. Total. 
A.hamaiiiihiffla., — lh‘811 2’8G ihl’uG 
A.ik'ihIhIu var. 
uiahraUi .. 79T> — 17*51 2*3‘) 99* tO 
A. HCatiH .... 7G 97 — 17*88 4*59 99*11 
Acacia ho/iiahjilif/Iia, A. t’lmn. ; ‘IT. FI.,’ ii., 383, 
The common “gidgoe," found in South Amei'ica, 
Victoria, and New* South Wales. This tree yields 
gum copiously throughout the summer season. 
My sample outwardly resembles, in a striking 
uiannei*, common pine re.sin or “ rosin.” Its fracture 
is conchoidal and very lustrous. F^rom its reseiu- 
bianco to “rosin,'' its colour is a drawback, but it 
is remarkably bright aud clean, and as it is so freely 
soluble, and so adhesive, it would well pay to ex- 
port, could it be obtained in sufficiently large quan- 
tities. It dissolves entirely in cold water, forming 
a very pale yellow, almost perfectly transparent 
liquid. 
Mr. Edward Palmer Jb*oc. Hoy. Soc., New South 
Wales,' 1883, 9‘1), states that gum of this species is 
eaten by the l)‘acks of Nortlioru Queensland, but 
there is apparently some confusion in the locality, 
I am not aware that this species extends to that 
colony. 
Acacia pcndnla, A. Gunn., var. Olai^cafa, F. v. M. 
Perhaps co-extensivo in geographical distribution 
with the normal species. A. !'«/•/•«/<. ” Hample ob- 
tained from between tlie Lachlan and Darling Ri- 
vers, Now Soutli Wales. 
^riiere is a marked difference between the new aiid 
the old gum of this sample. Tho new gum is in 
1‘ounded pieces, and very similar in appearnaco and 
Jjaual size to Senegal gum, and Aden gum arabic. 
rile gum which remains long on the trees becomes 
filled with minute fractures which cross each other 
Nearly at right angles. 'Bho fissures wliich radiate 
from tho centre of a lump cause the lump to break 
jnto sub-triangular or conical pieces, but as disin- 
tegration proceeds, these pieces are broken down into 
ftniall angular fragments. It is worthy of notice tliat 
the colour of the lumns varies in depth from the 
Centre outwurds, and tlie bands of colour are usually 
lairW Well defined. Tho difference in colour is de- 
pendent upon tho extent to which the fissiiring has 
proceeded. As fissiiring (the result of weathering) 
most evident on the outside of a lump, and as 
"C process of repeated reflection of light makes the 
part affected lighter in colour, though more opaque, 
lie colour of the gum increases in depth as the 
coiitral portions of a lump are i*eached. A common 
int for the outside (or basal portion) of a conical 
piece is amber, that of tho inside (or apical portion) 
“rosin brown.” I have described these appearances 
at some length, because they are commonly seen in 
tho “dry country” gums. 
Lilie other Wattle gums, this would require se- 
lecting for the market, but some portions are of 
veiy nigh class. It dissolves entirely in cold water, 
forming a perfectly clear solution, almost colourless, 
with the exception of a brownish tint. 
Acacia ticnti.s, F. v. M., *11. FI,’ ii., ,%0. — Found 
in all the colonies, except Ta.smania ; “ prickly wat- 
tle.” Sample obtained from Whittabranali, Tiboo* 
buna, New South Wales. 
Tlic trees of this species in the above neighbour- 
hood are for the most part very small, and gum is 
found on them very sparingly. Afuch of it is of a 
rich amber colour when frcsnly exuded, and quite 
different in appearance from any other Wattle gum 
I have seen up to tlio present. Other portions are 
nearly as pale as selected Turkey gum arabic, while 
a small portion is of a dainty sulphur-ycilow colour. 
It is sparkling and clean-looliing, and "would be a 
very acceptable article of commerce could it bo ob- 
tained in quantity. This gum presents more points 
of resemblance to tho preceding than to any other 
gum yet examined by me. It is very easily reducible 
to a powder, partly on account of its somewliat 
ve.siciuar nature, ft dissolves in cold water readily 
and completely, forming a solution of a pale yellow- 
ish-brown or amber coloxu*. — /‘Iiarmaceattcal JourmU 
8(JItL’lJ KXTKUMLNATGK. 
I have tho lionor to give an account of an experi- 
ment I made last .\pril on pricklv-pear, with a small 
quantity of the .\ustialian Scrub I^xterminator noticed 
in G. O., dated .5th October 1889, No. 2287.L. 
2. The manufacturers of the chemical very ob- 
ligingly sent me, oil my application, a sample, ir>-lb. 
weight, free of cost, througli Messrs. Oakes Sc Co. 
3. 1 made two experimeuts, tlie first on the 18th 
and tho second on 28th April, on prickly-pear growing 
on an open niece of ground to tho south-east of tho 
Dindigul road, just outside tlie toll-gate, tho clump 
of pear selected on each occiwion being vigorous, old 
ana well developed. 
4. Fic.A c.rpcriuunf. -The first experiment I need 
not dwell on. I used a small garden hand-syriugo 
to throw the fluid over the pear. The suckers 
in the syringe were loose, a great part of tho 
fluid escaped, and was wasted, and it could not 
be scattered sufficiently. I used 3 Ib, of the chemical, 
2 lb. in 8 gallons of water, tliat H, at 1 to 4, and 1 lb. 
in 3 gallons, that is, at 1 to 3. The only points that 
the experiment established were (1) that the chemical 
destroyed tho parts of the pear that were well sprinkled, 
and (2) tliat tlio strength of tho fluid appeared to 
make no difference in its destructive effect, that at 1 
to 4 being just as effective as that at 1 to 3. 
5. Second c.ci,cci,iic)it.~ThG second expevimout was 
more complete. For this, I got the loan of a small 
hand fire-engine from the Bonth Indian Railway 
Workshop. The engine was a Itttlo too big to get 
full value out of the quantity used, for the long 
tube from the engine held some two gallons of the 
fluid when the engine had ceased to work ; hut it 
answered well otherwise. The remaining 13 lb. of 
the chemical were put into 52 gallons of water, that 
is, at 1 to 4^, and pumped on the pear. When the 
engine ceased to work, tho fluid iii the tubing wat* 
poured off, and pumped on, as well as possible, with tho 
garden svTiii^e; and w'Uen that was done, a small part 
of the choiiucal found undissolvod in the bottom was 
mixed with a further quantity of water at about 1 to 
20, I should say, or weaker^ though this could not 
bo meaHuved accurately; and this very weak solution 
wiui thrown over a separate small clump of young 
pear growing near. ° 
As in Australia, tho clieinical produces no 
immediate effect on the pear. Two days after tho 
experiment, a top leaf here and there hung down 
slightly browned; on the third day, though there was 
a siuart shower of rain iu the night previous, tho 
beginning of decay was well marlcod ; and. by the 
