1 8 MICROSCOPIC PLANTS. [CHAP. 



placed fragments of the leaves on which- they had 

 developed their secondary spores on young, but full- 

 grown, Berberry leaves, under the same atmospheric 

 conditions. In from twenty-four to forty-eight hours 

 a quantity of the germinating threads had bored 

 through the walls and penetrated amongst the sub- 

 jacent cells. This took place both on the upper and 

 under surface of the leaves. Since, in former experi- 

 ments, it appeared that the spores would penetrate 

 only in those cases where the plant was adapted to 

 develop the parasite, the connection between P. 

 graminis and ALcid. berberidis seemed more than 

 ever probable. In about ten days the spermogonia 

 appeared. After a time the cut leaves began to 

 decay, so that the fungus never got beyond the 

 spermogonial stage. Some three-year-old seedlings 

 were then taken, and the germinating resting spores 

 applied as before. The plants were kept under a 

 bell glass from twenty- four to forty-eight hours, and 

 then exposed to the air, like other plants. From the 

 sixth to the tenth day, yellow spots appeared, with 

 single spermogonia; from the ninth to the twelfth, 

 spermogonia appeared in numbers on either surface ; 

 and a few days later, on the under surface of the 

 leaves, the cylindrical sporangia of the ^Ecidium made 

 their appearance, exactly as in the normally de- 

 veloped parasites, except that they were longer from 

 being protected from external agents. ... It seems, 

 then, indubitable so far that AZcidium berberidis does 

 spring from the spores of Piiccinia graminis" 



Other experiments have been made in which the 

 spores of <Lcidium have been placed on healthy 



