242 DISEASES OF THE COTTON PLANT. 
This disease has been attributed to leaving pokeberry 
plants in the field. But this I have never observed, and 
suppose the assumption to be on the same principle that 
the mildew on wheat was formerly attributed to the influ- 
ence of the barberry bush. Others state that rust is owing 
to an undue proportion of lime in the earth, and it is 
no doubt caused by some organic or inorganic imperfection 
of the soil in which it is grown ; but until such soil shall 
have been thoroughly analyzed, and its component parts 
correctly ascertained, nothing certain can be known about it. 
There is also another theory in regard to the subject of the 
rust — that it is entirely owing to atmospheric changes, and 
not to the soil. Experiments, however, ought to be insti- 
tuted to find out the real cause, and the result made 
known, as the disease has done, and is at present doing, 
much injury to the crops of the South. Salt, sown at the 
rate of half a bushel to the acre among cotton, is stated to 
be a certain preventive of tbe rust, and to restore the plant 
to its former vigor; but several planters whom I have 
spoken to on the subject, deny the fact, and say that salt 
had no effect whatever. 
There is also another species of rust caused by an 
acarus, which vdU be found described on a preceding page. 
SHEDDING OF TOUNG BUDS, OB BOLLS, CAUSED BT WET 
WEATHER. 
When the cotton blooms, or flowers, are exposed to the 
heavy and beating rains of a Southern climate, especially 
between the hours of ten and two, as they are opening, or 
have already opened, it frequently happens that such blooms 
prove barren. The outer calyx turns yellow, and eventually 
the unfertilized flower and immature boll fall to the ground, 
the seeds turn brown, and the fibre of the cotton is worth- 
