INJURIOUS AND OTHER FUNGI. 35 



germinate, the filaments enter the tissue of the leaves, and in the 

 course of a few daj'S make themselves manifest on the under sui'- 

 face of the leaves, in what are known as "cluster cups." The inte- 

 rior of these pretty little cups is closely packed with spores of a still 

 different kind, which are called the cecicUum spores. These in 

 turn will not grow upon the barberry, but when they fall upon a 

 blade or stalk of grain, they soon germinate and produce the yellow, 

 rusty covering so often seen, caused by a multitude of another form 

 of spores, called uredo spores, clustered upon the surface. In this, 

 the true rust state, the fungus first consists of minute filaments, 

 which run in all directions through ,the tissue of the grain plant, 

 stealing its nourishment as they go, and is ifoticeable to the naked 

 eye onlj^ when these threads break through the epidermis and bear 

 the j^ellow or orange uredo spores. The rapid and destructive de- 

 velopment of this fungus depends much upon the weather. Should 

 there be a series of warm showers, or a muggy atmosphere, just at 

 the time the grain plant begins to form its grain, the growth of the 

 rust plant is especially favored. It absorbs rapidly the food which 

 is on its wa}^ to the seeds, and uses it up in producing a vast num- 

 ber of spores upon the surface of the leaves and stalks, at the ex- 

 pense of an empty head of husks at the top. Later in the season, 

 from the uredo state the final perfect teleutospores are produced, 

 thus completing the circuit of life in this little rust plant. Long be- 

 fore rust was discovered to be a plant, farmers had noticed that 

 there was a close relation between it and the barberry ; and at 

 present the latter is being rapidly destroyed, with good results, 

 though it can scarcely be expected that the rust plant wiU thereby 

 become extinct, as probably the a^cidium state grows on other plants 

 than the barberry, though not as yet discovered elsewhere. 



Tliis plant is an excellent illustration of potymoi-phism, so common 

 among fungi, and it also answers well to show the vast number of 

 spores these microscopic plants produce. The teleutospore usuall}^ 

 bears from five to ten sporidia ; and allowing onty one of these to 

 find the barberry leaf, there may be from one to fift}' clusters as a 

 result. In this case suppose onlj^ one, and a very low estimate for 

 its contents would be 250,000 aecidium spores, and if only one of 

 these in a thousand finds a place on the grain stalk, and each brings 

 forth its 250,000 fold, there would be, under such circumstances, 

 62,500,000 from the single one from which we started. Taking the 

 same teleutospore, and supposing every spore in all the stages found 



