June r, 1882.] 
THE TROPICAL 
AGRICULTURIST. 
1061 
tent at the Government tanneries at Hoonsoor, and 
at the Artillery tanneries at Bangalore. 
[Cawia auriculata, and its qualities and uses, have 
been frequently noticed in our columns. It grows 
plentifully in the Jaffna Peninsula, where we have 
seon its foliage used for manuring the cultivated 
lands. The properties of its bark are also well-known 
to the fishermen. We do not see why plantations of 
the shrub could not profitably be formed. We re- 
commend the idea to enterprizing natives in the north 
and east of the island. Even Europeans might find 
it worth attention. Dr. Bidie embodied much valuable 
information on the subject in his Melbourne Exhibi- 
tion list, which we noticed at the time — August 1880. 
We should like to know the price ut which the bark 
is quoted in Madras, as well as that of the thorny 
acacia which grow plentifully in the woodlands of 
the north and east of Ceylon. — Ed.] 
MR. FORBES LAURIE ON HYBRIDS. 
It is all very well for Mr. Forbes Laurie saying 
"more anon," but while he is incubuting we are in 
danger of being driven insane. We had scarcely issued 
our article dwelling ou the fact thut the singularity 
of " G. robusta," identical with ft Lanova, and C- 
pubescens, was that, if a hybrid, as most planters 
believed, its seeds produced seedlings true to type, 
when the following letter reached us, shewing that, 
in the opinion of the great advocate of the hybridity 
theory, the seeds of hybrids do not come true to type : — 
Leangapella Estate, Rangala, April 20th; 1882. 
My deak Sir, — In your editorial of 18th inst. I see 
we have another name for newly-discovered cinchouas, 
found among others under cultivation. As a very 
careful reader of Mclvor's reports aud the Indian Blue 
Books on cinchona, I was under the impression that 
neither Pubescens nor Lauossa came up true to seed, 
and this was tho only complaint there was against 
them. I cannot believe in any specially true form, and, 
from the mauy analyses I have had made, I find hybrids 
(spurts, if you will, or any line names) differ vastly in 
the bark value. . A very fine hybrid by no means 
uncommon in Ceylon, C. Calisaya Angliea, yields lesa 
quinine than succirubra, and an old tree very much 
resembles a Pubescens. There is also a very fine hybrid 
(to look at) which also resembles Pubescens, and which 
from the roundedjform of the ends of its leaves I conclude 
to be a cross with Pahudiaua, which has that pecu- 
liarity more than any cinchona I know. It is one 
of the handsomest and poorest of cinchona trees, yield- 
ing not more than '90 of quinine at 4 years old. Now 
1 very much want to know to what variety or form 
Magni/olia has beeu given. The finest leuves I have 
always seen grown from Micrautha seed varied in 
character, but all the plants were very robust ingrowth 
Also what is "Robusta"? Among tho many analyses 
of hybrids I possess, there are none of high value 
without a marked resemblance to either some of the 
Officinalis forms or to Ledge riana, aud those very 
robust are often worthless, although resembling tho 
finer kinds. Ono very handsome glabruus form at 4 
j ears old gave "GO of quinine. A good Pubescens 
selected from a clearing grown from seed (wh#re only 
Succirubra and Officinalis are growing) gives on 
Howard's analysis S'.'U quinine sulphate with hardly 
any other alkaloids. More anon. — Yours truly, 
Wm. Fokiies Laurie. 
How is a poor editor to preserve his five wits in the 
midst of a discussion where no principle is adhered 
to? Mr. Win. Smith, thot giant l'hilistian, uill ol 
course triumph, both iu Cath and in thu Catck of 
Askelon, crying out : " Did I not tell you ? Forbes 
Laurie is a vera clover callant, but he canna impeach 
tho wisdom of the Creator by proving that He per- 
mits the confusion of hybridization." We hold that 
it is for Mr. Forbes Laurie to reply, and not for 
the editor of the Observer, who simply gave up his 
long cherished opiuions on evidence which he deemed 
to be unquestionable, 
What Mr. Broughton said about hybrids (the pro- 
duction of which he did not deny) was that they 
partook of the bad qualities of both parents aud the 
good properties of neither. That opinion so discouraged 
Mr.McIvor that he, for a time, gave up his experiments. 
But he resumed them, and, out of a number of worthless 
hybrids, selected and grew C. pubescent, which gave 
to Howard's analysis 10 per cent of alkaloids. It is 
very true that the seed did not come true to type 
in producing trees equal to the original, but trees 
were produced, superior to the one parent (succirubra) in 
quinine and to the other (officinalis) in robust habit 
of growth ; and our impression was that for several 
generations C. robusla had come fairly true to seed. 
Mr. Laurie's letter sends us all to sea again, and 
we must really ask him to lose no time in telling 
us all he knows about hybrids : their reality ; their 
quality ; and their permanency or evanescence. We 
have no pet theory to support, we are merely anxious 
to obtain and publish the truth. 
" GRAPHITE " OR "PLUMBAGO." 
The important admission is made in the recently 
published Economical Geology of India that, at the 
present clay, nearly all the plumbago of commerce 
comes from Ceylon. We were told of finds in Aus- 
tralia, and we are constantly hearing of deposits in 
Siberia, Canada, the United States, and elsewhere. 
But either the mineral is imperfect as a carbon, or 
mixed with grit aud impurities. The labour question 
is also an important factor in the question, and, 
although India is specially favoured in that respect, 
there seems at present no danger of Ceylon losing her 
practical monopoly in really good, pure plumbago. 
The ouly pity is that the demand for the article is 
not susceptible of more rapid expansion. Pure' graph- 
ite, it appears ranges from 95 to 99 per cent of 
carbon, so that a perfectly pure piece may be said to 
be wholly composed of carbon. If we could now only 
discover the process of converting this pure carbon 
into diamond. Heat, pressure and •' magnetism" are, 
probably, the chief agents of the conversion of nu opaque 
body into a crystal. It is not merely the abundance of 
the mineral in Ceylon but its general purity which 
gives our island the monopoly of thetrade. For cylin- 
ders aud lubrication, as for pencils, gritin the carbon is 
bad. Our plumbago has literally, not metaphorically, 
no grit. Wo quote Mr. Ball's sum mary notico : — 
Graphite or Plumbago: Central Ken aiks. — Pure 
graphite, as found native, contains from !»."> to per 
cent, of carbon. The commercial values of the differ- 
ent qualities ordinarily found depend upon the amount 
of impurity winch they include. Foreign matters can 
bo got rid of by grinding, washing and the use of 
acids, and the purified product ni be employed for 
all the purposes to which graphite is applied, but tho 
process 1* couth, as tin- .-ni.ilh ,i |..u:u.t.-. v\ .uv 
