AMERICAN INSTITUTE. 451 



my microscope lias proved ineontestibly that it is owing to the yellow mag- 

 got, derived from the egg of the midge deposited in the blossoms of the 

 wheat in June. They are the cause of the abortion of the ovary, so that 

 the grain can never advance beyond the state at which it had arrived at the 

 time the flower first expanded. Wheat is subject also to mildew, smut and 

 rust. The former, when examined under the microscope, indicates the 

 presence of exceedingly minute plants of the mushroom tribe, known as 

 fungi, which grow upon the stem and leaves, and rapidly exhaust the juices 

 of the plant. Finding one field of wheat on my farm abounding more in 

 mildew than another, I was induced, microscope in hand, to search out the 

 cause, and found several barberry bushes in the vicinity covered with mil- 

 dew. They were removed, and the prevalence of disease with them. 

 When wheat is infected by smut, the integuments of the farina of the grain 

 are converted into black powder, which, if wet with water and examined 

 through the microscope, will present to view an enormous number of trans- 

 parent globules of viscous fluid, covered with a membrane. And I have 

 proved it infectious, by placing it upon healthy stems at a distance, which 

 were not only attacked by the disease, but conveyed it to the seed, which, 

 when sowed the following year, produced smutty plants. 



Rust is another disease that prevails much in some districts. It is a 

 brown dust, produced by a parasitical plant. The poisonous substance 

 known as ergot in rye, is produced by a fungus plant. The smut in barley, 

 when examined by the microscope, is shown to be an entirely different spe- 

 cies from that in wheat, and though I could readily prevent it in the for- 

 mer by salt brine and lime, I could not remedy the evil in the latter by 

 any application. 



My microscope hints to me that all the grasses are subject to unmistaka- 

 ble diseases, all resulting from attacks of parasitic fungi, animalcules, and 

 insects ; and I can only explain it on the ground that they contain a very 

 large amount of nitrogenised matter. At all events they offer to the agri- 

 culturist a fertile theme for reflection and observation. Grasses are chiefly 

 injured at the roots from the larvjxj of the cockchaffer, which always carry 

 on their work of destruction below the surface of the ground. Tlie lady 

 bird (Cocconella impunctata,) and the moth (Liparis,) do great damage 

 above ground. Insects obtain their food from the most extensive pasture 

 grounds ; from the majestic maple to the insignificant moss — all the plants 

 in the universe are brought into requisition to feed and maintain them ; 

 every part of every plant, however nauseating, poisonous, or pleasant it may 

 be, yields them provender. Some attack the roots, others the branches and 

 stems, others the leaves and flowers, others still the fruit; no plant, or part 

 of a plant escapes them, so declares the microscope. The potato disease is 

 caused by an insect. And in my opinion it will yet be discovered that the 

 cholera, yellow fever, small pox, and other epidemics, are caused by in- 

 sects, which attack at the same period and in the same district, all those 

 whose constitutions at the time are ripe for their inception, after which 

 they gradually diminish, and finally disappear. 



