112 



"ROYAL HORTICULTURAL SOCIETY. 



pointed out the identity of rust and mildew, at a time, be it ob- 

 served, when the accurate study of these parasites was in its 

 infancy, and when people were inclined, with Unger, Fries, and 

 others, to regard them as mere growths from the cellular tissue, 

 and not as distinct specific organisms. 



A very important point in De Bary's memoir is the distinction 

 which he draws between Puccinia graminis and Puccinia straminis, 

 because the latter is more especially addicted to wheat than the 

 former ; and should it be found on further experiment that its 

 winter spores do not produce the JEcidium on barberry-leaves, 

 many of the anomalous cases will at once receive a good explana- 

 tion. The TTredo, or rust of P. graminis, is much later in its ap- 

 pearance than that of P. straminis, the latter frequently occurring 

 in spring, while the former does not appear till the end of May or 

 June, and sometimes later. The TTredo -spores of P. graminis are 

 oblong, with four pores for the exit of the germinating-threads ; 

 those of P. straminis nearly globose, with six pores. Moreover, 

 the resting-spores of the latter are not contained in the same 

 sorus with the rust-spores, but in especial sori covered with the 

 cuticle. They are in general clavate, the lower division longer 

 than the upper ; they are close pressed to each other, and in con- 

 sequence have many sharp angles. Their peduncle is always 

 shorter, and often much shorter than one of the divisions. The 

 margin of the sorus bears a number of light brown prismatic 

 paraphyses, and a few are scattered over the disk. In Puccinia 

 graminis the divisions of the spores are nearly equal, and the 

 upper division blunt, while the whole is free from angles. 



These distinctions require a very careful reexamination, and it 

 is much to be wished that our author should complete his very 

 useful experiments, by trying whether the winter spores of P. 

 straminis, like those of P. graminis, are capable of developing the 

 JEcidium on the barberry. 



There are many other points of interest in the memoir, but 

 rather of a botanical than horticultural interest, though some- 

 thing like just views as to the real nature of these parasites is 

 absolutely necessary to the cultivator. 



