Nov. 1, 1899.] 
Supplement to the " Tropical Agriculturist.^' 
363 
explained, but the above observations indicate 
that these substances, like starch, cellulose, and 
sugar, are derived from foreuic aldehyde, which 
as already explained, is assumed to be the primary 
substance from which all plant substances are 
built up. The formation of acids in plant tissues 
is explained moie easily than that of fatty sub- 
stances and resins. When starch or sugars are 
subjected to the action, of dilute nitiric acid, oxalic 
acid is produced. Similar treatment of other sac- 
charine bodies results in the production of tartaric 
acids. Plant acids are due to a partial oxidation 
of neutral substances. When the carbohydrates 
oxide at a low temperature, or the penetration of 
oxygen into the tissues of the jilant is interfered 
with by the structure of the organs, combustion 
of the neutral substances is not complete, i.e., they 
are not reduced to carbon -dioxide and water. In 
this case, the oxygen combines with the sub- 
stances to produce acids. For example, consider- 
able amounts of oxalic acids and oxalates are 
found in the juice of the cactus, especially the 
prickly pear, which is but slightly permeable to 
air. When, therefore, the volume of oxygen ab- 
sorbed is greater than of carbon oxide evolved, 
it may be assumed that oxygen has been fixed by 
organic compounds in the plant to produce acids. 
These acids, then, are derived from neutral sub- 
stances by oxidation, and, consequently, trace their 
ultimate origin to the decomposition of the carbon 
dioxide in the chlorophyll cells. In the experi- 
ment to which attention was called at the begin- 
ning of this article it would have been impossible 
to grow peas without adding a few cubic centi- 
metres of an infusion of fertile soil to the sand. 
If this precaution were not observed with the peas, 
or if the seed of some non-leguminous plant were 
used, the experiment would be a failure- The 
seed would produce a sickly plant which would 
soon die of starvation due to the absence of one of 
the elements — nitrogeii — necessary to its develop- 
ment. Although the leaves of plants grow in an 
atmosphere four-fifths of which is nitrogen, they 
are entirely incapable of directly utilising this 
element. 
The process by which the free nitrogen of the 
atmosphere is utilised by plants has only been 
explained in comparatively recent years. Hellriegel 
and Wilfarth in 1886 reported experiments which 
demonstrated the ability of Leguminosae to attain 
normal development in soil absolutely deprived of 
organic matter, the only precaution necessary being 
the addition of a small account of an infusion of 
fertile soil. A few weeks after the addition of the 
infusion the roots of the leguminous plants were 
covered with tubercles, which microscopic examin- 
ation showed to be filled with micro-organisms. 
Breal has shown that inoculations may readily 
be made with these organisms by pricking a tuber- 
cle with a needle and then inserting it into a 
growing root. 
The tubercle bacteria have been cultivated and 
their products have recently been brought into 
commerce under the name of "Nitragin,"' which 
is used for supplying these organisms to soils 
which are deficient in them. The growth of 
leguminous plants in sterile sand depends upon 
the presence on their roots of tubercles filled with 
these organisms. Through their agency the plant 
is supplied with nitrogen for the production of 
nitrogenous matter, so that if the mineral elements 
are present in sufficient quantity the plant makes 
normal growth. The plant profits by the nitrogen 
furnished by the bacteria, while the latter utilise 
the carbonaceous matter supplied by the plant, 
thus establishing a symbiosis. Although the pro- 
cess of fixation" of nitrogen by the organisms and 
its utilisation by the plant has not yet been clearly 
explained, we can understand how that, notwith- 
standing the great quantities of nitrogen carried 
away from the soil with every cutting of lucerne 
or clover, the amount of nitrogen in the soil 
increases rather than decreases. 
MEMS. ABOUT FRUITS. 
The proper manipulation of trees in transplanting 
is a subject about which most people know very 
little. It is not uncommon to see trees furnished 
with masses of roots and planted with the utmost 
care, prove failures. Those who have had tlie 
greatest experience in this matter advice that 
fruit trees with the roots pruned back are more 
successful than trees with the ordinary supply. 
We generally find severe pruning of roots practised 
in transplanting cocouiit palms, but the same 
practice is avoided when fruit trees have to be 
dealt with. Why this difference in the treatment 
of transplanted trees ? 
It is well known to gardeners that an injured 
root is a source of decay in a transplanted tree, and 
that the best thing to be done under the circum- 
stances is to remove the injured portion by 
means of a clean cut. A clean cut wound is easily 
healed over but not so a jagged one. Now in 
transplanting it is idle to expect that the roots— 
however carefully they may be treated — will escape 
injury. After transplanting, it is not until the 
roots throw out new white fibres that they are of 
any use to the tree, and it is well known that 
these fibres are sooner developed from pruned 
than from unpruned roots. 
The selling price of plantains in the London 
market does not appear in the usual price lists of 
tropical produce. It is, therefore, interesting to 
find in an Exchange, a note to the effect that in 
July last though the arrival of bananas in 
London was heavy, the demand was equal to 
the supply, and the price ranged from 7 to 10 
shillings per bunch. 
It is astonishing with what pertinacity a name, 
no matter how enormous and absurd, will stick to 
a thing after once it has come into general use. 
Professor Van Denan, the well-known pomologist, 
referring the name "grapefruit" as applied to 
the pumelo, expresses the hope that intelligent 
fruit growers would abandon the absurd and in- 
appropriate name " grapefruit " and use in its stead 
the proper name " pumelo." " What relation," he 
asks, " can there be in that large citrus fruit to 
the grape? Every one that knows anything of 
pomelo, except it be the most ignorant tyro in 
pomology, knows there is none. Then why per- 
petuate such nonsense ? The fruit is called pomelo 
or pumelo in its native East Indian home ; and it 
is called the same in the books on pomology ; yet, 
