348 
THE TROPICAL 
AGRICULTURIST. [October i, 1881. 
differs in allied genera) and the appearance of the 
larvae, which are yet in an early stage, they would 
seem to belong to a species of Aspidiotus, or some 
allied insect of the Coccidae kind. The genus Aspi- 
diotus I comprises several species, which, in America 
and Europe, are injurious to fruit trees. Gishurst's 
compound has been found a very effective means for 
the destruction of all kinds of "scale insects." 
I have read a paragraph in the Herald respecting 
the supposed appearance in New Zealand of the Color- 
ado potato beetle. I have seen several species of 
beetle here which were suspected to be the potato 
beetle, but I have never yet seen the true beetle 
amongst them. If you or any of your correspondents 
wish to see the real Doryphora decem-lineata, I can 
show you one, and an inspection of a specimen is 
often better than even a good coloured plate. — R. S.] 
WATTLES FOR TANNING-. 
Sir, — Being anxious to collect some good seed, I 
am at a loss to know how to tell that which Js the 
best. That black and golden varieties are the best 
1 learn from the report of the Wattle Bark Com- 
mission, and while the broad long leaf enables the 
golden to be easily distinguished, nothing that I met 
within the report enables me to distinguish the black 
from the silver or other varieties. I find that bark 
strippers are not at all agreed about the names of this 
tree. In my ramble, I meet with a black bark, a green 
bark, a bark covered with white spots, rough and smooth 
barks— trees on creek banks, flats, and ranges. Except- 
ing the golden the leaf in all appears to me alike. I have 
been told that a while flower distinguishes the silver 
wattle, and that the bark with white spots is silver 
wattle ; but I observe this latter bearing a yellow 
flower, while the white flower I have not seen at all. 
Pertinent to the information I am seeking, does it 
matter whether the seed be taken from a young or 
an old tree, from the bank of a river or mountain 
side, or a tree with extensive or sparse blossom on it ? 
Schoolboy. 
[The real black wattle, or true tanning variety, is 
the acacia delbata. The silver wattle, which is con- 
sidered inferior to the black, is the acacia mollissima, 
which can be easily distinguished by the silver appear- 
ance of the under part of the leaf, and the glaucous ap- 
pearance of the bark ; the flowers^ of the latter are 
a bright yellow, that of the former a dirty yellow. 
The silver Wattle is in general found on the banks 
of creeks, the black wattle on high dry 'ground. 
The black has rough bark, the silver being comparat- 
ively speaking smooth. The seed, so long as it is 
good, may be gathered from any tree. — Ed.] 
QUALITIES OF VARIOUS SOILS. 
Sir, — In your issue of June 28 a "Selector" asks 
for an opinion upon the probable virtues of soil 
formed from the ddbris of granite ranges. Although 
neither an agriculturist nor directly connected with 
the tillage or cultivation of land, I have pretty large 
opportunities of observing the effect of various modes 
of agricultural treatment as applied to various soils, 
and also of notiug their various natural products ; 
it may, therefore, not be deemed presumptuous on 
my part to offer an opinion. I feel bound, then, in 
the first place, to take some exception to your own 
remark that "the character of the timber attests at 
least a fair amount of fertility in the soil," I be- 
lieve it is a pretty generally accepted proposition 
that limber trees depend but little upon the mineral 
son bituents of the soil for their nourishment and 
growth, an opinion which appears to be borne out 
by the well-known fact that, whereas a given weight 
of grain, straw, or other such-like vegetable sub- 
stance yields on burning a considerable residuum of 
unvolatilised ash ; timber, on the other hand, yields 
almost no residuum. Certainly some slight qualifi- 
cation of this general statement is necessary in the 
case of the Australian eucalypti, inasmuch as they 
contain an excessive amount of potash as compared 
with other timber trees. But this fact will hardly 
affect the general argument. At all events, observa- 
tion has led me to the conclusion that depth of soil, 
aspect, and shelter are much more potent factors in 
the production of timber than character of quality 
of soil. It is true that trce3 of large size, or of 
value for the purposes of the sawyer or splitter, are 
rarely or never found in localities where the soil is 
thin and the rock near to the surface ; but it is 
equally true that timber of the finest quality is com- 
monly produced on soil too poor to be of any use 
for the growth of ordinary farm crops, provided only 
that the other conditions are favourable. The yullies 
and ravines that furrow the lower slopes of our mount- 
ain ranges are the principle habitat of the larger 
eucalypti ; and it would seem that if only the soil 
be deep enough to afford the roots complete protec- 
tion from the summer heats and a permanent supply 
of moisture, and if the aspect and situation be such 
as to insure shelter from violent storms, all the con- 
ditions necessary for the growth of timber are fulfilled, 
and that the quality of the soil has really not much 
to do with the matter. Of the trees mentioned by 
your correspondent, stringy bark, white gum, yellow 
box and wattle are all to be found growing on the 
slopes of Mount Alexander, where the soil is granitic 
and of very poor quality ; also on the poor granitic 
soils in the parishes of Laugley, Baynton, and Cobaw, 
to the north-east of Kyneton, and on the granitic 
and schistose soils of that portion of the Macedon 
State Forest recently thrown open for selection. They 
are also to be found growing equally, though I think 
not more, luxuriantly on the rich volcanic soils form- 
ing the upper portion of the Macedon Range, and on 
similar soils in many parts of the Bullarook and 
Wombat State Forest ; aud again in the fertile soils 
of the tertiary formations of South Gipps Land and 
the Western Port district. Red gum I have never 
known to grow except in the near neighbourhood of 
rivers and watercourses — the best specimens usually 
in situations liable to occasional partial inundation. 
I think, also, that red gum is not to be found in 
• Victoria at an altitude greater than about 1,200 feet 
above the level of the sea, although on this point I 
cannot be certain. Adverting now to the subject- 
matter of your correspondent's letter, he requests an 
opinion upon a statement which has been made to 
. him to the effect that a couple of crops will tho- 
roughly exhaust the fertility of granitic soils, and 
leave them incapable of producing even grass. Well, 
as farming is conducted in Victoria, and is likely 
to be conducted for some generations to come, I 
think the above statement may be accepted as liter- 
ally true. Whereas our volcanic soils will generally 
staud cropping for 10 or a dozen years before they 
begin to show signs of failure, and the best tertiary 
soils may be reckoned on for probably an equal length 
of time, it is a fact that the best granite soils will 
not yield more than a third crop, and generally not 
more than a second. And, further, whereas the richer 
soils will, after an exhaustive course of grain crop- 
ping, still continue to bear grass of at least some 
value, the exhausted granite soil after like treatment 
will remain for some years as bare of useful herbage 
as a macadamised road. Of course there are degrees 
of poverty even in granite soils. For example, in 
Cobaw, Langley, and Pyalong, Glenhope, Baynton, 
Elphinstone, and Ha-rcourt, these soils are poorer than 
the granite soil in the parish of Kerrie. In the latter 
locality it is more tenacious, probably from the fact 
that it contains a larger proportion of feldspar, while 
