701 



together with the corn and grass which it infects ; but the best and 

 most complete account is that given by Sir Joseph Banks, in 1805, 

 which, at the time of publication, was largely circulated among agri- 

 culturists, and which really exhausted the subject, leaving nothing 

 more to be learned respecting its history. The pamphlet is intituled 

 * A short Account of the Cause of the Disease in Corn called by Far- 

 mers the Blight, the Mildew, and the Rust.' Every part of the his- 

 tory of this minute parasitic fungus was traced ; and beautifully 

 accurate figures of it, in all its stages, accompanied the description. 

 I will attempt to give an outline of the discoveries of Fontana and 

 Banks, as far as confirmed by my own observations. 



Sir Joseph Banks prettily observes that a plant, being fixed in 

 the ground by its root, is diflFerently circumstanced from an animal 

 which can move from place to place. The plant must have its nutri- 

 ment, of whatever kind, brought to it; the animal travels from place 

 to place in search of its food. The food of the plant is fluid ; the 

 food of the animal is solid. The mouths of the plant are innume- 

 rable ; they are distributed over its whole surface ; they are exces- 

 sively minute, and only to be seen by the aid of the microscope : 

 their presence, form, and peculiarities have long been familiar to the 

 botanist, although it is now considered that I'espiration rather than 

 nutrition is the function for which they are intended ; they are shut 

 in very cold and very dry weather, but open in wet weather ; and 

 when the weather is at the same time wet and warm, the plant is in 

 the very best stale to receive its atmospheric supplies. Such is the 

 character of what are called by botanists exogenous or endogenous 

 plants ; and wheat, barley, oats, and rye are endogenous plants. 



There is another class, or division of plants, called thallogenous. 

 Amongst these are what are vulgarly called funguses, mushrooms, toad- 

 stools, puff-balls, &c. A very great number of these are minute and 

 parasitical, or living on other plants. These are increased by seed, 

 which is so excessively small as to float about in the air. If we break 

 open a puff"-ball, we may see millions on millions of these little seeds, 

 issuing forth like smoke from the bowl of a tobacco-pipe. In the lat- 

 ter part of summer the air is filled with such seeds ; and in warm and 

 moist weather their quantity is increased tenfold. The blight of the 

 wheat is one of the smallest of these funguses ; and its seeds are of 

 course infinitely smaller than the fungus itself. 



We have, then, a field of wheat, in waim, damp, summer weather, 

 opening its pores, or mouths, to receive the moisture. We have at the 

 same time a damp atmosphere, charged with countless myriads of the 



