216 
Supplement to ike " Tropical Agriciitiurist." [Sept. 1, 1899. 
■n-oulcl en.able the Veterinary Surgeon to telegraph 
advice at once, and state whether he were able to 
give ])ersonal attendance to tlie case or not, and 
tlierehy save valuable time, which is always of 
imjjortance in acute and urgent cases." 
ORKJIN AND FORMATION OF ORGANIC 
MATTER IN PLANTS. 
(CoJitinued.) 
It does not suffice to ktiow tliat the leave>, 
saturated with water, absorb the carbon dioxide 
of the air, and under the influence of the sun's 
rays evolve oxygen. It is necessary to define this 
process and to explain how organic matter is 
derived from the product of this decomposition. 
Maquenne and the author, in the article already 
referred to, report the result of studies on the 
quantities of carbon dioxide absorbed by leaves, 
taking into account also the quantities which 
would be absorbed by a volume of water equ.il 
to that contained in the leaves under experiment. 
The results, as already stated, indicated that the 
absorption is not simple solution of carbonic 
anliydride in the water of the leaves, but a 
chemical combination of the dioxide witii water 
to form the acid GHaOa. This carbon dioxide 
decomposes in the leaves, giving off a volume of 
oxygen (O,) equal to that of the carbonic anhy- 
dride absorbed as observed by Boussingault, and 
leaving a residue of formic aldehyde (CH^O.) 
The fact that formic aldehj'de has never been 
found in plants might be taken as casting doubt 
upon the correctness of the above hypothesis, 
but the hypothesis is strengthened by the fact 
that the molecules of this aldehyde combine 
easily with each other, and although we do not 
find formic aldehyde itself, we may safely assume 
that some at least of the bodies present are the 
result of combinations of molecules of formic 
aldehyde. 
As a matter of fact, bodies which might be thus 
formed are extremely abundant in the vegetable 
kingdom, as will be seen hereafter. It is known 
also that the aldehj'des combine readily with 
oxygen and hydrogen, and it is of great interest 
to ascertain whether there are not p)resent in 
plants some products thus derived from formic 
aldehyde. As a matter of fact such substances 
have been found. By oxidation formic aldehyde 
yields formic acid, which gives to nettles their 
irritating properties. The addition of hydrogen 
to formic aldeliyde in i^roper proportions yields 
methyl alcohol, which Maqueune found in all the 
plants which he studied. While the presence in 
plants of these two compounds so closely allied 
to formic aldehyde supports the hypothesis of 
the formation of this aldehyde in the chlorophyll 
cells at the moment of the 'decomposition of the 
carbon dioxide by the sun's rays, there are other 
proofs of a more convincing nature. The reduc- 
ing sugars are widely distributed in plants. 
Loew, and later Fischer, startitig with formic 
aldehyde, havi; ])repared these sugars artificially. 
They succeeded in linking together six formic 
aldehyde molecules, and tliiia formed a reducing 
sugar ruscmbling those found in plants. This 
b-'autiful synthesis convinced the physiologists 
that the primary organic compound from which 
all the others are derived is formic aldeliyde 
produced by the decomposition of the hydrated 
carbon dioxide. Many other compounds common 
in plants are formed by the combinations of mole- 
cules of formic aldehyde, such as glycerin, which 
exists in all oils aud which contains three mole- 
cules of formic aldehyde combined with hydrogen ; 
the gums, v>'hich readily yield a sugar containing 
five molecules of formic aldehyde; and persite, 
found in the fruit of the alligator pear which 
contains seven molecules of the aldehyde. Starch 
is easily transformed into glucobe by simply hea'- 
ing the starch with weak acid solution. This in 
fact is the method employed in the commercial 
pi eparation of glucose. Starch is also transformed 
into glucose during germination by the action 
of a ferment present in the seed. This change is 
so easy and so frequent that there is no doubt 
that the transformation could be reversed ; that 
is, the glucose cculd be changed into starch. Up 
to the present time, however, tliis has not been 
done by purely chemical means, but when leaves 
are jilaced in a solution of glucose, starch soon 
appears in them. The starch is formed from the 
glucose through the combination of several mole- 
cules of the latter, water being eliminated. 
Starch is very abundant in leaves which have 
been exposed to sunlight. Its presence is more 
easily detected than that of glucose. The latter 
is but a transition stage, while the starch is 
reserve material which remains in the tissues 
much longer than glucose. The starch which is so 
abundant at the end of the day disappears during 
the night. The leaf is thus seen to be both 
a laboratory and a store-house which is conti- 
nually emptying and filling itself. The starch 
disappears from the leaves in the form of glucose. 
Aditlt plants utilise this transfer form of starch 
in the formation of cellulose, just as young plant- 
lets utilise the glucose formed from starch in the 
cotyledons of the seed during germination. The 
different steps have now been traced in the forma- 
tion of the organic matter of plants from tlie 
simple carbon dioxide absorbed to jtlie complex 
carbohydrates of the plant tissue-. It only 
remains to briefly discuss the derivation of some 
particular forms of these carbohydrates. Among 
the most important of these is cellulose, which 
forms the envelope of the cells and which is easily 
charged into reducing sugars under the action of 
acids. It appears during the germination of seeds 
simultaneously with the disappearance of starch. 
There is little doubt that it is derived from 
glucose, and consequently from formic aldehyde. 
J t seems clear, therefore, that all the carbohydrates, 
the gums, sugars, starch, inulin, and cellulose 
originate in the activity of the chlorophyll cells. 
The same is probably true of the tannin and resin 
groups. There are, however, certain plants which 
contain a group of sugars known as the inosites, 
which are true carbohydrates, but whose mole- 
cular construction is different from that of the 
other glucoses, since their derivatives belong 
to the aromatic series and not to the fatty acid 
series, to which the other groups belong. There 
is one other important point which needs some 
explanation. If we study the phenomena of 
