DE BABY ON MILDEW. 



Ill 



JEcidia. The rust was most abundant where the wind carried 

 the spores. The following year the same observations were re- 

 peated ; the spores of the JEcidium were collected, and applied to 

 some healthy plants of rye. After five or six days these plants 

 were affected with rust, while the remainder of the crop was 

 sound. 



In 1863 some winter rye was sown round a barberry-bush 

 which in the following year was infested with JEcidium, which 

 was mature in the middle of May, when the rye was completely 

 covered with rust. The first traces appeared on the 26th. Of 

 the wild grasses near the bush, it was the twitch {Triticum 

 repens) which was the most affected. The distant plants of rye 

 were free from rust. 



The spores of the JEcidium would not germinate on barberry- 

 leaves ; the barberry JEcidium could not therefore spring from 

 some previous JEcidium. The Z7mfo-spores of Pueeinia graminis 

 on germinating penetrate into the parenchym of the grass on 

 which they are sown ; but on barberry-leaves, if the tips of the 

 threads enter for a short distance into the stomates, their growth 

 at once ceases and the leaves remain free from parasites. 



The resting-spores of Puccinia graminis, when applied to leaves 

 of Bhamnus frangula and Bhamnus cathartica, do not penetrate 

 the parenchym nor produce any parasite, therefore its yEcidium 

 cannot be a member of its cycle ; but whether it is connected 

 with the JEcidia of other plants, as that of the nettle, is at present 

 matter of doubt. 



Montagne has, however, described a Puccinia Berberidis, on 

 leaves of Berberis glauca from Chili, which grows in company 

 with utEcidiwn Berleridis. This at first sight seems to contradict 

 the above conclusions ; but the JEcidium which from the same disk 

 produces the Puccinoid resting-spores, appears to be different from 

 the European species, inasmuch as the cells of the wall of the 

 sporangium are twice as large and the spores decidedly of greater 

 diameter*. The resting-spores, moreover, differ not only from 

 those of Puccinia graminis, but from those of all other European 

 species. 



It does not seem necessary to go into that part of the memoir 

 which relates to the history of the supposed connexion between 

 the two parasites. De Bary, however, seems not to be acquainted 

 with the remarkable memoir of Professor Henslow, in which he 



* It is very doubtful whether these characters are of any real importance. 

 The size may vary in plants growing on different individuals. — Ed. 



