296 PROCEEDINGS OF THE 



that Uredo linearis and Puccinia graminis of wheat were but stages 

 in the development of JEcidium Berberidis of the barberry. Till 

 recently his results were usually ignored, denied, or doubted in 

 Britain. In 1881 Dr. Charles B. Plowright, of King's Lynn, 

 instituted a series of experiments which he has continued during 

 last year, and these have verified the accuracy of de Bary's obser- 

 vations. He adopted every precaution to guard against error, and 

 his results, I need hardly add, may be implicitly relied on. Not 

 only did he sow spores of JEcidium Berberidis on wheat, but of 

 Puccinia graminis on barberry, and in the one case came up Uredo 

 linearis, in the other, JEcidium Berberidis. In the light of this 

 knowledge it is interesting to trace the life-history of the parasite. 

 First, growing in hedge or copse is a barberry bush. On the under- 

 side of its leaves appear cluster-cups, on the upper-side the flask- 

 like spermogonia. The cluster-cups ripen and the spore at the tip 

 of each chain goes off and is superseded by the one next it, which 

 has in turn to make way for its successor, and so on. The aecidio- 

 spore thus thrown upon the world either finds some kind of grass 

 on which it can grow or perishes without fulfilling its mission. 

 Should it fall in with a young blade of wheat, it begins work, 

 sends out a filament that searches about till it hits on a stoma, into 

 which it insinuates itself. The part of the germinating filament 

 inside the leaf thereupon swells out and branches, the contents of 

 the spore flow through into this enlarged space, and thus the 

 parasite gets inside to work havoc. Its mycelium spreads through 

 the tissue, and in about a week it sends up every here and there 

 multitudinous tufts of thread-like branches towards the surface of 

 the leaf, which burst through the epidermis, producing spores that 

 fill the ruptured parts in reddish mass. The minute roughening on 

 these spores probably helps to fix them to any blade of wheat on 

 which they may fall, and their lightness permits every breath of air 

 to disperse them. During nearly the whole season they are pro- 

 duced and dispersed, and, falling on wheat plants, give out tubes 

 that bore their way inside, and plunder, and, from their mycelia, 

 reproduce spores of a similar kind. But towards the end of the 

 season, when a chill comes into the air and a rigidity to the grasses, 

 we could almost imagine that the parasite had become stricken with 

 a presentiment of futurity. It gives up producing rust spores, and, 

 to save itself from annihilation, slips into another alternation of 

 generation. It produces dark, hard, heavy teleutospores, attached 





