July 1, 1902.] 
THE TROPICAL AGRICULTURIST. 
15 
of cultivated plants a? a sure way ot increasing 
the yield and quality, and alcex<ly ra^nlts have been 
achieved sufficiently reniirkable to encouraste much 
hope for the future. One of the roost striking ins- 
tances is furnished by the Sugar-Beet, which in 
Garrap.ny, in ISSfl, contained only five per cent, 
of sugar, and now furnishes not much less than 
fifteen per cent. Duiing the same time the gross 
yield of roots per acre has increased by about fifty 
per cent., so that the ou'put of sugar per acre is 
now over four times as great as seventy years ago, 
a result for which careful breeding is chiefly ac- 
countable. 
In this and other countries much has been ac- 
complished in the matter of plant improvement, but 
much undoubtedly remains to be done. It is work 
that makes no exceptional demands on capital or 
skill, as is proved by the fact that many of our 
best varieties of plants, especially vegetables, flowers, 
and fruits, have been raised by amateurs, in not a 
few cases by cottagers. It is, however, work that 
requires much perseverance, and at certain seasons 
much attention ; though the demands that it makes 
on time necessarily depends upon the extent to which 
it is carried on. For its successful performance it 
requires inteligent observation, a knowledge of the 
gardener's or farmer's requirements, delicate manipu- 
lation, and accurate recording, rather than strenuous 
exertions. 
Two main lines are usually pursued to produce 
a new and improved variety of crop-plant. One 
method of producer, which has been successfully 
adopted by some of the best known workers, is to 
make a careful examination of the individual plants 
in crops cultivated in the ordinary way, and frooi 
these to make a selection of those that are distin- 
guished by superior merits Snrh superiority 
may take the form ot yield, capacity to tiller, a 
high percentage of starch as in Barley and Potatoes, 
or of sugar as in the case of Turnips, Swedes, and 
Mangolds), capacity to ripen early, to resist disease, 
&c. But whatever may be the object selected, it 
must be kept steadily in view, and all individual 
in the progeny that fall short of the character 
that may have been set up must be carefully 
eliminated. By intelligently pursuing such a system 
of selection during a series of years, a distinct 
type or variety will be produced. 
The other method commonly pursued begins by 
artificially crossing two individuals whose superior 
qualities it may be desirable to unite in a single 
variety. The seeds that result from sucli a 
cross are shown, and it is generallj' found that the 
resultant plants are extremely mixed in character. 
Many are inferior to either of the parents, others 
occupy an intermediate position, while a few may 
be superior to both. It is the latter only thai are 
reserved f'lr subsequent cultivation, and from their 
proaeny also many individuals must be eliminated. 
In the course of time, however, the percentage of 
inferior individuals becomes smaller and smaller, 
until, at last, the variety comes true to type. 
In the main, these two systems of improvement 
are the same. The plants selected in the first case 
may be natural crosses, while in the second they 
are artificial crosses, but the improvement is, in 
both cases, completed by selection. The larger the 
number of plar.ts selected or of crosses effected, the 
greater are the chances of a really valuable new 
variety being found and for this reason it is desirable 
to work with largo numbers, though, of course, one 
may be fortunate in producing a valuable variety 
even when the work ia being carried on but on a very 
small scale. 
In sowing pedigree seeds, the soil should as a rule 
be of good quality, so that the resulting plants may 
have the opportunity to produce the maximum yield. 
But it is of even greater importance to arrange mat- 
ters so that each individual plant is placed in 
possession of precisely the same conditions of growth. 
, Only in this way can we be sure that the appearance 
9£ superior qualities in the progeny ia due to some. 
thing inherent in the plant itself, and not to the 
specially favourable character of the situation where 
it has been grown. 
Farmers have generally given moro attention to 
the breeding of animals than ot plants, but just 
beciuse less has been done in the latter field, 
more probibly remains to be accomplished. It is 
surprising- how quickly a single plant multiplies, it 
the conditions bo made as favourable as possible. The 
Late Mr. Shirrefi gives an instance from his own 
experience. In the spring of 1819 he found a specially 
vigorous whiat plant in a field on his farm in 
East Lothian, and he resolvetf to propagate it. He 
therefore removed tlie plants in its neighbourhood, 
and gave it a dressing of manure, the result being 
that, notwithstanding some damage by hares, he 
harvested from this single plant 63 ears, containing 
2,473 grains. In the following autumn these grains 
were dibbled in wide rows in a suitable piece ot 
ground, and in the two succeeding seasons the pro- 
duce was sown broadcast. The result was that the 
fourth harvest from the original plant yielded 42 
quarters of seed, which was subsequently placed on 
the market under the name of lilungoswells Wheat. " — 
Gardeners' Chronicle, 
CENTRAL AMERICAN RUBBER. 
It is generally considered that Central American 
rubber is the product of Gastilloa elastica Cervantes, 
described and figured in the West Lidtan Dullelin, 
Vol. II, pp. 101-3. The tree has a variety of lo"ai 
names the most important of which are ' Hule ' or 
•Ule' and 'Oaucho.' Distinct from this plant ia 
C'astilloa Tumi, Humsley (Hooker's Icones Plantarnm 
plate 2.561^ a tree also found in Central America 
and sometimes confused with the true Central 
American rubber tree which it closely resembles in 
general appearance. In an article which appeared in 
the Beiliefte zum Tropenpllanzer for July 1901, Mr. 
Th. F. Koschny, a pUuterof long experience in Cost a 
Rica, distinguishes the following varieties of ' Hule ' 
trees : 
Castilloa elastica ; 
' Hule bianco ' White rubber tree. 
' Hule negro ' Black rubber tree. 
' Hule Colorado ' R?d rubber tree. 
Castilloa Tumi : 
' Hule tunu ' ' Gutta percha.' 
The names of the three so-called varieties are given 
from th-? colour _ of the bark of the tree. ' Hul- 
Blanco ' is described as the only one v/orth cultivoe 
tion, giving iiiick and abundant latex. The tree is 
not shade loving, being seldom found in forests, and 
not easily injured by tapping. ' Hule negro ' gives 
a watery latex, and that of ' Hule Colorado ' whilst 
good, is scanty. 
Mr. Koschny suggests that ' Hule Colorado ' may 
have been introduced into Java and Cevlon, and 
be the reason for the comparatively small returno 
given by Central American" rubber trees in thoss 
islands. This point was touched upon by Dr. IMorris 
in his Cantor Lectures on the ' Plants yielding Com- 
mercial India Rubber' to the Society of Arts in 1898, 
'The plants distributed from Kew and now under 
cultivation in various tropical Colonies would be more 
correctly termed, according to their place of origin 
Darien ''Castilloa" or Darien " Caucho " trees. Thia 
would distinguish them from the Ule trees of Mexico 
British Honduras, and Nicaragua, and indicate their 
history. It is Possible that there is no great difference, 
if any, in the quality of the rubber yielded by these 
trees, but so far no one has undertaken a compara- 
tive investigation of the produce.' 
The Ceylon plant has been considered as possibly 
belonging to the species Castilloa J/arihamiana 
Markham, (Circular No 11, Botanic Gardens Ceylon)^ 
On the other hand in the Kevj Bulletin, for "Sept' 
1901, Mr. W. B. Hemsley slates that Castilloa JIark 
hamiana is not distinguishable from Castilloa elastica 
Careful comparison at Kew between typical speoi- 
mens of the rubber tree from British HoudarB. 
