February i, 1892.] 
THF TROPICAL AGRICULTURIST. 
5«3 
native habitats 3'ield gums more or loss insoluble, 
produce more soluljle products when grown in sonic 
otlier countries. The question is a wide one, and 
well worthy of being followed up, for it would be of 
the highest commercial importance if it could be 
shown that free-yielders of inferior metarabic gum 
would in other soil and climate develop a tendency 
to the formation of arabic gum (see A. dea/liata, 
A. di'iuii'i-fiis). 
Some notes by Dr. Hopff on an Australian Wat- 
tle gum as compared with guui arabic will be found 
in i'hanii. Juiini., vii., 588. The experiments have no 
conclusiveness, and the source of the Wattle gum is 
not given, for it was probably unobtainable. 
I have nivided the Wattle gums experimented 
upon into three provisional groups. I could make 
sagacious guesses as to the groups into v/hioh many 
other Wattle gums are likely to fall, but prefer to 
confine myself to the record of facts. The classifi- 
cation of the future will probably be into arabin and 
nietarabin groups, in which case my groups II. and 
III. will simply require to be imited. The samples 
chosen for analysis were picked ones in all cases. 
Group I. (Arai3ian Group.) 
Acucla lioinalo/ilii/lla. 
Acacia jiendula. 
Acacia .scntin. 
They are readily and entirely soluble in cold 
water, like Turkey gum arabic, for which they form 
an excellent substitute. Arabin . is their character- 
istic and niain constituent. Following are analyses: — 
Arabin. Metarabin. Moisture. Ash. Total. 
A. Jiomahnh i/Ila... 79-84. — 16-83 2-86 99-5^ 
A. perichda var. 
i/lahi-ata .. 79'5 — lY'Sl 2-39 99-40 
A.sentiH.. .. 7(5 97 — 17-88 4-59 99-44 
Acacia humaloplii/lhi, A. Cunn. ; ' B. Fl.,' ii., 383. 
The common "gidgee," found in South America, 
Victoria, and New South Wales. This tree 3 i elds 
gum copiously throughout the summer season. 
My sample outwardly resembles, in a striking 
manner, common pine resin or " rosin." Its fracture 
is conchoidal and very lustrous. From its resem- 
blance to "rosin," its colour is a drawback, but it 
is remarkably bright and 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 (' Proc. Eoy. Soc, New South 
Wales,' 1883, 9-1), states that gum of this species is 
eaten by the b acks of Northern Queensland, but 
there is apparently some confusion in the locality, 
as I am not aware that this species extends to that 
colony. 
Acacia pciuhda, A. Cunn., var. Glahrata, F. v. M. 
Perhaps co-extensive in geographical distribution 
with the normal species. A. " Yacian." Sample ob- 
tained from between the Laclilan and Darling Ri- 
vers, New South Wales. 
TMiere is a marked difference between the new and 
tlie old gum of this sample. The new gum is in 
rounded pieces, and very similar in appearnace and 
usual size to Senegal gum, and Aden gum arabic. 
The gum which remains long on the trees becomes 
filled vvitli minute fractures which cross each other 
nearly at right angles. The fissures which radiate 
from the centre of a lump cause the lump to break 
into sub-triangular or conical pieces, but as disin- 
tegration proceeds, these pieces ai-e broken down into 
small angular fragments. It is worthy of notice that 
tlio colour of the lumps varies in depth from the 
ciMitre outwards, and the bands of colour are usually 
fairly well defined. The difference in colour is de- 
pendent upon the extent to which the fissuring has 
proceeded. As fissuring (the result of weathering) 
is most evident on the outside of a lump, and as 
tlic process of repeated rcHcction of light makes the 
part affected lighter in colour, though more opaque, 
tlio colour of the gum increases in depth as the 
central portions of a lump are reached. A common 
tint for the outside (or basal portion) of a conical 
piece is amber, lliat of the inside (or apical portion) 
" rosin brown." I have described these appearances 
at some length, because they are commonly seen in 
the " dry couutr-y " gums. 
Like other Wattle gums, this would require se- 
lecting for the market, but some portions are of 
very high class. It dissolves entirely in cold water, 
forming a perfectly clear solution, almost colourless, 
with the exception of a brownish tint. 
Acacia :ienti.i, F. v. M., 'E. F!,' ii., 3(50.— Found 
in all the colonies, except Ta.smania ; " prickly wat- 
tle." Sample obtained from Whittabranah, Tiboo- 
burra, New South Wales. 
The trees of this species in tlie above neighbour- 
hood are for the most part very small, and gum is 
found oi;i them very sparingly." Much of it is of a 
rich amber colour when freshly exuded, and quite 
different in appearance from any other Wattle gum 
1 have seen up to the present. Other portions are 
nearly as pale as selected Turkey gum arabic, while 
a small portion is of a dainty sulphur-yellow colour. 
It is sparkling and clean-looking, and would be a 
very acceptable article of commerce could it be ob- 
tained in quantity. This gum presents more points 
of resemblance to the preceding than to any other 
gum yet examined by me. It is very easily reducible 
to a powder, partly on account of its somewhat 
vesicular nature. It dissolves in cold water readily 
and completely, forming a solution of a pale yellow, 
ish-brown or amber colom-. —PhannaccuJical Journal 

SCR UB EXT URMINATO R. 
I have the honor to give an account of an experi- 
ment I made last April on prickly-pear, with a small 
quantity of the Australian Scrub Exterminator noticed 
in G. O., dated 5th October 1889, No. 2287-L. 
2. The manufacturers of the chemical very ob- 
ligingly sent me, on my application, a sample, 15-lb. 
weight, free of cost, through Messrs. Oakes & Co. 
3. I made two experiments, the first on the 18th 
and the second on 2Sth April, on prickly-pear growing 
on an open piece of ground to the south-east of the 
Dindigul road, just outside tlie toll-gate, the clump 
of pear selected on each occasion being vigorous, old 
and well developed. 
4. Firsi r.ciierii„rid.~The first experiment I need 
not dwell on. I used a small garden hand-syringe 
to throw the fluid over the pear. The suckers 
in ^ the syringe were loose, a great part of the 
fluid escaped, and was wasted, and it could not 
be scattered sufSciently. I used 3 lb. of the chemical, 
2 lb. in 8 gallons of water, that i^, 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 the parts of the pear that were well sprinkled, 
and (2) that the strength of the fluid appeared to 
make no difference in ila destructive effect, that at 1 
to 4 being just as effective as that at 1 to 3. 
5. Second c.r.iH-riincnf.—The second experiment was 
more complete. For this I got the loan of a small 
hand fire-engine from the South Indian Railway 
Workshop. The engine was a Itttle 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 ; but it 
answered well otherwise. The remaining 12 lb. of 
the chemical were put into 52 gallons of water, that 
is, at 1 to 4?f, and pumped on the pear. When the 
engine ceased to work, the fluid in the tubing was 
poured off, and pumped on, as well as possible, with the 
garden syringe ; and when that was done, a small part 
of the chemical found undissolved in the bottom was 
mixed with a further quantitv of water at about 1 to 
2iJ, I should say, or weaker, though this could not 
be measured accurately ; and this very weak solution 
was thrown o^v a separate small clump of youn" 
pear growing near. " ° 
ti. As in Australia, the chemical produces no 
immediate effect on the pear. Two days after the 
experiment, a top leaf here and there hung down 
slightly browned ; on the third day, though tliorewas 
a smart shower of rain in tlie niglit previous, tlie 
beginning of decay was wvW marked; and, liy the 
