10 



rKKlXlSPOKKS 





: 



Fig. 10. Leaf of Carex 

 pendula, with uredo- and 

 teleuto-sori, slightly en- 

 larged. 



four) germ-pores ; in tact, tin- uredo- resembles the aecidiospore 

 in character, and musl b»- <-<>nsidered as homologous with it— 

 the stalk-cell corresponding to the intercalary cell of the latter. 

 But they differ considerably in the fad that the uredospore is 



always produced singly, uot in chains. 

 (This is not true, however, of all 

 the Uredinales.) The membrane of 

 the uredosjxiiv is nearly colourless, but 

 it encloses a bright orange granular 

 and oily mass, with two nuclei. Every 

 cluster of uredospores produced on the 

 same spore-bed is called a sorus ; it is 

 surrounded by the lacinise of the epi- 

 dermis, which is more or less torn or 

 split by the enlarging mass. In many 

 cases, several sori become confluent 

 and form a larger pustule (Fig. 10). 

 In other species of Uredinales the uredospores have coloured 

 membranes or possess a larger or smaller number of germ- 

 pores. Moreover the distribution of these pores over the 

 surface is characteristic for each species : they may be placed 

 equatorially, as they are in P. Garicis (Fig. 11), or towards 

 the poles, or scattered over the surface with regularity or 

 without any order. 



A uredospore may be very easily detached from its pedicel, 

 and conveyed (chiefly by wind, though sometimes by insects) 



to another leaf of Carex, on which it 

 germinates, the germ-tube enters a stoma, 

 produces a fresh crop of mycelium and 

 another sorus of uredospores ; this process 

 can be repeated indefinitely. The my- 

 celium can also grow up and down the 

 leaf, producing fresh sori in its course ; 

 for this reason the sori are usually 

 arranged in linear series, owing to the 

 parallel venation of the Carex-leaf. The germ-tubes of the 

 uredospores are often curled or branched like those of the 

 ;ecidiospores, and the germination is of the same character in 



Fig. 11. A uredospore 

 which hasgerrninated, 

 showing the three 

 germ -pore s. x 600. 



