60 MANUBRES. 
developed, and may be made eventually hereditary by care 
in keeping the individuals possessing them, through succes- 
sive generations, under the influence of the agents by which 
those special forms or qualities were originally induced. 
Have we not here, then, in this material, the means of 
producing, within a single season, an influence which the 
labors of a century in hybridization directed to the im- 
provement of the same qualities, might not have effected, 
and the promise also of rendering permanent, and of im- 
proving to the highest degree, those qualities when once 
implanted? If broom corn is but sorghum with the sac- 
charine quality undeveloped in it by reason of its subjection 
to natural influences constantly exerted, may we not appre- 
hend a slow but sure deterioration of the best varieties of 
the latter that we have, unless some such powerful agent as 
this is laid hold of to check the tendency to gradual de- 
basement ? Sulphate of ammonia has been found to exert 
an influence very similar to that of the sulphate of lime 
upon clover. 
The mode in which the gypsum acts in producing this 
change is not understood. Liebig, after many years of 
assiduous research, expresses his inability to answer satis- 
factorily this question. He regards its action as very 
complex. He has lately found, however, that it promotes 
in a remarkable degree the distribution of potash and mag- 
nesia in the soil, by the substitution of those bases for the 
lime in the combination with sulphuric acid, thereby mak- 
ing them soluble, and rendering ‘nutritive elements ac- 
cessible to and available for the clover (at least) which 
were not so before” (Liebig, ‘“‘ Nat. Laws of Husbandry,” 
p. 327). That it also fixes ammonia is certain. Prof. 
S. W. Johnson estimates that its presence in the juice of 
plants has the effect of checking undue evaporation from 
the leaves, thus enabling them to resist drought in a high 
degree. 
