APRIL 29, 1897 | 
NATURE 
611 
and the Apocynacee, as will be seen from the following 
summary. 
EUPHORBIACE® (Hevea brasiliensis).—This is the 
source of the Para rubber already referred to, and the 
plant from which the earliest supplies of rubber were 
obtained when, in 1770, it first appeared in London as a 
new discovery for rubbing out pencil marks on paper, 
and realising about three shillings per cubic inch. At 
the beginning of the present century it began to be used 
in the treatment of woven fabrics, for air-tight and 
waterproof articles. So rapidly, indeed, did its use 
develop, that in the year of the Queen’s accession Para 
rubber was imported into England to the amount of 
141,735 pounds, and twenty years later it had increased 
to 3,477,445 pounds ; while at the present time, when the 
trade returns are counted by hundredweights instead of 
pounds, the import accounts for 1896 showed the total of 
rubber from all sources to be 431,164 cwts., which were 
valued at 4,993,180/. The species of Hevea of which 
Hi. brasiliensis is the best known as a rubber pro- 
ducer are large trees, growing abundantly in the humid 
forests of tropical America, especially along the Amazon 
and its tributaries. As in most of the Euphorbiacee, the 
wood is soft and easily cut in the tapping process. The 
trees are locally known as Seringas. //. brasiliensis 
grows to a height of 60 feet, branching from the base. 
The collection of the milk commences about August, and 
is continued till the following January or February. In 
the wet season the milk is too watery to produce good 
caoutchouc. The trunk of the tree is wounded with a 
knife or a small axe-like instrument, a deep horizontal 
cut being first made a few inches from the base, and a 
vertical one from this, some distance up the trunk ; oblique 
cuts are then made into this main channel, which conveys 
the milk into small clay vessels placed at the bottom to 
receive it. As these are filled they are emptied into a 
calabash or gourd, and when this is full it is carried to a 
more convenient place for coagulation ; for this purpose, 
the contents of the calabash are emptied into a large 
earthenware basin. A kind of wooden paddle, with a 
widish blade and a long handle, is then dipped into the 
milk, and turned about over the smoke and heat of a 
fire made of the hard bony fruits of Waximiliana regia, 
or Attalea excelsa, which fire is enclosed with a thick 
earthenware covering, open at the top, like a small 
chimney, to allow the heat and smoke to escape. As the 
rubber coagulates upon the blade, in the form of a thin 
film, more milk is poured over it, and the same operation 
of holding it over the fire repeated. This goes on till a 
sufficient thickness of rubber is deposited, when it is cut 
through round the edge, and the paddle withdrawn. 
Various kinds of Para rubber are thus prepared, and are 
known in commerce under different names, according to 
the thickness of the deposit. The large round balls, 
generally knownas “ Negro-head,” are made up of scraps 
of rubber tightly rolled together. This kind is often much 
adulterated, and one specimen in the Kew Museum con- 
tains in the centre, as shown when cutting the ball 
through, about one-third its weight of pieces of brickbat 
and cotton cloth. 
Besides the process here described, some Para rubber 
is coagulated by the aid of alum, and by other means; 
but the quality of the rubber from this source is always 
good. 
So far back as 1873, the necessity of securing supplies 
of rubber for future generations occupied the attention of 
the Kew authorities, and living plants of Hevea brasili- 
ensis were sent to India, with the view of establishing the 
plant in that country. Smaller consignments were also 
made to the West Coast of Africa, Jamaica, Dominica, 
Trinidad, Queensland, Singapore and Java. The history 
of this important undertaking is fully recorded in the 
Reports of the Royal Gardens, Kew, for 1873, and sub- 
sequent years, where, indeed, will also be found recorded 
NO. 1435, VOL. 55] 
the various experiments made by Kew in the intro- 
duction of other rubber-yielding plants into countries 
that were thought suitable for their extension. 
Another rubber-yielding plant of the Euphorbiacez is 
that which furnishes the kind known as Ceara Scrap, 
from the fact that this kind always appears in commerce 
in masses composed of agglomerated scraps. The plant 
is a native of Central America, and is known to botanists 
as Manihot Glaziovit. In 1876 a large quantity of seeds 
and plants of this species were collected in Central 
America, and brought to Kew; they were rapidly propa- 
gated, and plants were sent to Ceylon, Singapore, 
Calcutta, and other places, in most of which the plants 
grew rapidly and yielded rubber, thus proving their 
capability of establishing themselves in their new homes. 
URTICACEH —In this order we find also a Central 
American rubber plant in Cas¢é//oa elastica, which, with 
perhaps some allied species, furnishes the commercial 
kinds known as Guatemala, Mexico, and West India 
rubbers. C. elastica is one of the species that has re- 
ceived much attention at Kew, and in 1876 was widely 
distributed. The Indian source of rubber (/7cus e/astica) 
also belongs to this group of plants. The plant is so 
well known as a parlour plant in this country, producing 
its fine glossy leaves under almost any conditions, that 
the fact is scarcely realised that in India and Ceylon it 
produces a veritable forest of trunks, and covers the 
ground with its long-stretching buttresses or roots, 
which run sometimes for distances of 30 or 40 feet. 
It is the source of Assam rubber, which is col- 
lected by wounding the stems and buttresses in all 
directions. The milk is collected either in holes made 
in the ground, or into leaves folded in the form of a 
vessel to receive it. On the upper parts of the stems, or 
on the branches, the juice is allowed to coagulate by 
exposure. The largest yield is obtained in August, when, 
on an average, a tree will give about 50 ozs. of milk, yield- 
ing about 154 ozs. of pure rubber. To prepare it for 
market it is sometimes poured into boiling water, and 
stirred until it is sufficiently firm to be carried about 
without sticking together. It is shipped from Calcutta in 
baskets made of split rattan, and mostly covered with a 
gunny bag. When cut the rubber has a mottled 
appearance, and is composed of pieces varying from. 
cream, or flesh colour, to a bright pink, or even red. It 
is either in the form of separate stringy-like balls,. 
irregular blocks, or large masses. . a 
Another species of Ficus, namely, /zcus Vogelzt, 
furnishés one of the kinds known as Lagos rubber. The 
tree is-known in West Africa as the “ Abba,” or “ Abo,” 
and is fully treated of in the Kew Bulletin for 1888,, 
p- 253, and 1899, p. 89. The quality of this rubber was 
never considered very satisfactory, as it was more or less 
resinous, and was consequentiy used for mixing with. 
other kinds rather than by itself. Another kind of Lagos 
rubber has, however, since been discovered, which has. 
proved to be of superior quality, and is next described. 
ApocYNACE&.—To this order belongs the several 
species of Landolphia, climbing, branching, shrubby 
plants, supporting themselves on the surrounding trees. 
of the forest. The stems of these plants average from 
4 to 6 inches in diameter, and the principal species, 
furnishing what is commercially known as African 
rubber, are Landolphia owariensis, L. florida, and ZL. 
Kirkit. The quality of these rubbers, though mostly 
good, is by no means equal to the Para kind, but the dis- 
covery of a new source of Lagos rubber, from a tree 
known to the natives as the “Ire” or “Ireh,” has given 
a great impetus to the trade of the West Coast of Africa 
‘na rubber of extremely good quality. The A tcksia 
africana, unlike the species of Landolphia, forms a tree 
50 to 60 feet high, witha trunk averaging 12 to 14 inches 
>, diameter. It is said to be one of the most beautiful 
