164 BOARD OF AGRICULTURE. [Jan., 



dark patches and lines upon them. The dark spots are due to a 

 vast multitude of dark colored spores which have developed from 

 the interior and ruptured the epidermis, or skin of the leaf and 

 stem. These are the winter spores and germinate in early spring, 

 each one producing a crop of smaller spores. These spores find 

 their way to the leaves- of the barberry, and if there are no bar- 

 berry bushes, it may be to some other plant, where they germinate, 

 sending their filaments into the tissue of the leaf, and in the course 

 of a few days a yellow spot is formed on the barberry leaf, and 

 shortly after a number of minute cups are formed from the burst- 

 ing of the epidermis of the leaf. As these cups are close together 

 they are often spoken of as "Cluster Cups." Each cup is packed 

 with spores which are formed in rows and break from their attach- 

 ment, and are carried away by the wind. These spores soon find 

 their way to the growing wheat, upon the leaves and stems of 

 which they germinate and send their absorbing threads through the 

 plant tissue. 



After a short time these threads congregate at certain places 

 near the surface of the wheat leaf, and, in enlarging rupture the 

 epidermis, rapidly ripen the myriads of yellow spores which give 

 the rusty color to the parts affected, and the common name of rust 

 to the fungus. From these filaments, and in these same sj>ots, the 

 brown spores appear later in the season and close the cycle of 

 changes of this polymorphic fungus. 



This is a rather complicated story, but it will be understood if 

 we compare this rust fungus to an insect which presents itself in 

 the very unlike states of caterpillar, chrysalis, and butterfly. As 

 the insect has to pass through these several stages to complete its 

 career, so does this wheat fungus assume these unlike forms, living 

 in one state upon one host-plant, and in its next stage upon another, 

 until it has completed its round. From the fact that the plant in 

 its different states is very unlike in appearance, such fungi are 

 called polymorphic. It is not very long since the different states 

 of this fungus were each regarded as different fungi, and have 

 been described as distinct species. That the presence of barberry- 

 bushes in the vicinity of wheat fields had a direct relation to the 

 occurrence of rust, has long been maintained by grain growers. 

 Indeed, so strong was this belief that it has been incorporated into 

 the laws of some states, which have legislated the barberry out of 

 existence. It has been asserted that the rust was due to the pol- 

 len or flower-dust of the barberry, and scientific men in denying 



