J. W. REED ON UROMYCES PISI. 73 



orange-coloured patches or sori. The uredospores thus formed 

 germinate on other pea-leaves, and produce successive crops of 

 uredospores throughout the summer ; and finally, in the autumn, 

 the same mycehum produces a crop of teleutospores, which form 

 dark brown sori on the surface of the leaf, and these, as said 

 before, rest during the winter either in the soil or on the surface 

 in connection with the decayed leaves, producing in the spring 

 the pro-mycelial spores which inoculate the newly developed 

 foliage of the Spurge. 



The uredospores are spiny, of a yellowish brown, and 17 — 21 /x 

 (say the j^^q of an inch) in diameter. They are said to have 

 as many as six germ-pores, and never less than two. The germi- 

 nation and mode of attack on the host-plant are the same as in 

 the case of the fecidiospores. 



The teleutospores, darker in colour than the other forms, are 

 produced in all Uredinese, and generally at theu* period of decay. 

 No fully satisfactory explanation as to the causes which 

 determine their production at this period has yet been offered. 

 In some species this is the only form of spore known. They are 

 unicellular in U. pisi, this being the invariable rule in the genus ; 

 and there is not more than one spore developed at the end of 

 each pedicel. They are 28—30 x 17—20 fx (say the ^i^ of an 

 inch in theii' long diameter by y^Vo ^^ ^^ ^^^^ i^ their shorter 

 one). The teleutospores of all Puccinias are bi-cellular, and their 

 structure is most clearly displayed in two beautiful slides of 

 F. arundinacea and P. amorphce lent me for this occasion by Mr. 

 Massee. 



At the apex of the teleutospore there is a single perforation 

 only, or at any rate a thinning of the outer cell-wall which 

 looks like it, and it is through this that the germinating process 

 protrudes ; in other words, the exospore is pierced by the 

 endospore in germination. When the teleutospores are bi- 

 cellular the germ pore of the lower cell occurs just below the 

 median septum. This perforation, if it be such, is shown in one 

 of the slides under the microscopes. A section on the same slide 

 shows other accidental and very dark globose bodies, which must 

 not be confused with any stage of the XJromyces; they are 

 specimens of that very cosmopolitan fungus SpJictiToiheca 

 Castagnei, or hop mildew. 



The germ tube of the teleutospore does not form a mycelium, 



