ON THE CULTIVATION OF THE CUBA TOBACCO. 
313 
not be obtained from the air. Whence, then, does 
it arrive that a plant which has many leaves can 
not obtain from the air the food required for 
blooming, although it can do so if it has only a 
few leaves ? It has been hitherto supposed that 
the reception of food from the air was in propor¬ 
tion to the number and size of its leaves; and this 
is plausible, but the contrary is not. When a plant 
standing in a moist and shaded situation grows 
too luxuriantly, and will not flower, the reason is 
not to be sought in a deficiency of food, but rather 
in its superabundance, and its influence on the too 
luxuriant development of its vegetative organs ; for 
that will counteract the contraction of the axis and 
the metamorphosis of vegetative into floral organs. 
Another statement, however, shows how Liebig 
arrived at the above conclusion. He says that, 
after the completion of its leaves, a plant does not 
require more carbonic acid from the soil; and that 
even perfect dryness of the soil will not impede 
the completion of its growth, if the plant continues 
to receive from dew and air the amount of moisture 
required for the process of assimilation; and that, 
in fine, it will derive in a hot summer its whole 
carbon exclusively from the atmosphere. 
This assumption (says Dr. Mohl) is the result 
of an erroneous view of the fact, that in many 
plants—by no means in all—such organic sub¬ 
stances are employed for the development of fruit, 
as, having been prepared by the leaves before the 
period of flowering, have been deposited in the 
stem or other organs, and are subsequently con¬ 
veyed to the fruit. We know that some bulbous 
plants will fruit even when taken out of the soil. 
But general assertions, taken from special facts, 
can only lead to absurd conclusions. Let Professor 
Liebig cut plants in bloom above their roots, (un¬ 
necessary, he says, at that period,) and expose 
them to as much dew and rain as he likes, ana see 
what will happen ; or, as he is fond of experiments 
on a large scale, let him take the hay harvest for 
a test of this theory, which, after all, (concludes 
Dr. Mohl,) seems to be nothing more than a dis¬ 
torted and overdone copy of the doctrine of the 
development of plants given by Schwerz, in his 
treatise on Practical Agriculture, (Anleiitung zum 
Pract. Ackenbau, iii. 56.) 
Besides the formation of humus, Liebig adduces 
another reason for the rotation of crops, viz., the 
relation which plants bear to the inorganic con¬ 
stituents of the soil. As every plant deprives the 
soil of certain ingredients, it thus makes it unfit 
for feeding similar plants, until by subsequent de¬ 
composition a fresh amount of such ingredients is 
again set free. To this proposition (says Dr. Mohl) 
no one will object; but it has long been known. 
Having thus examined in detail the work of Dr. 
Liebig, Dr. Mohl concludes with the following 
general recapitulation. It appears upon the whole 
that Liebig has not availed himself of his chemi¬ 
cal resources to clear up doubtful points in the 
nutrition of plants. Contrary to the spirit of a true 
investigator of Nature, he has not formed his con¬ 
clusions on the detailed facts of vegetable pheno¬ 
mena, but on random observations, or vague oper¬ 
ations on a large scale, destitute of all precision. 
His calculations are based on arbitrary assump¬ 
tions. His book, therefore, far from being a con¬ 
sistent and well-digested theory, swarms with 
contradictions and false reasoning. He does not 
possess a knowledge of the most elementary doc¬ 
trines of vegetable physiology. His assertion that 
physiologists have hitherto considered humus as 
the chief food of plants, is untrue. The assump¬ 
tion that plants live merely on inorganic substances, 
is by no means new, but has long been one of the 
controverted points of vegetable physiology. The 
assertion that all botanists have doubted the ab¬ 
sorption of carbon by plants, by their decomposi¬ 
tion of carbonic acid, is untrue. The assertion that 
plants neither absorb organic substances, nor as¬ 
similate them, rests on mere theoretical speculation, 
and is destitute of all proof. The statements as 
to the relation borne to the atmosphere by plants 
in the dark, is in direct opposition to every fact 
bearing on the subject. The assertion that the 
nitrogenous food of plants, and that which con¬ 
tains no nitrogen, are absorbed in certain propor¬ 
tions, is uncorroborated by the analysis of either 
the seed or the full-grown plant. The theory of 
the rotation of crops, is contrary to experience, and 
unsound in its details. The assertion that plants 
receive their food during summer from the atmo¬ 
sphere alone, is incorrect. 
On the other hand, it can not be denied that 
Liebig’s idea that plants derive their nitrogen from 
the ammonia of the atmosphere, is very happy 
and pregnant with results. It is also probable that 
the absorption of saline bases is in direct ratio to 
the power of saturation of the acids formed in 
plants. These two views are a real gain to science, 
and it may be expected that his work will also 
have the merit of exciting others to make correct 
experiments on the nutrition of plants. But he 
has endeavored to introduce into vegetable phys¬ 
iology a series of most erroneous notions, and his 
unbecoming outbreaks against other physiologists, 
have proved him to be very little acquainted with 
the subjects on which his book is written. 
From, the Southern Agriculturist. 
ON THE CULTIVATION OF THE CUBA TOBACCO. 
Sir :—The following communication on the Cu¬ 
ba tobacco, is from a gentleman who has had op¬ 
portunities of becoming thoroughly acquainted with 
the mode of cultivating and curing the plant, as 
practised in Cuba, and where experience has ena¬ 
bled him to ascertain the modifications necessary 
to be adopted in transferring the culture to this 
country. It will be perceived that Gen. Hernandez 
estimates the value of the tobacco, in leaf, at 50 
cents per pound—a higher price than it usually 
brings in our markets, where it is purchased for 
the purpose of being used as wrappers for cigars, 
the fillings of which are generally of American or 
Virginia tobacco. It is well known, however, that 
the best tobacco raised in the island is never ex¬ 
ported, being reserved for the manufacture of the 
celebrated Havana cigars, after selling, as we have 
been informed, for more than a dollar a pound. 
As the tobacco raised and cured here, is considered 
by judges as no way inferior to the best Havana, 
it would probably sell for even a higher price than 
