CRYPTOGAMS 



365 



forms, in special fructifications or ^ectdia, germinate, like the uredospores, 

 directly after they have been set free. The secidia (Fig. 287) are small, at first 

 closed, but afterwards open and cup-shaped bodies ; they rupture the epidermis 

 of the host-plant, and contain a hymenium of closely-crowded mycelial branches 

 from which chains of round or polyhedral spores are produced by a process of septa- 



Fig. 288. — Piiccinia graminis. 1, Transverse section through a grass-haulm with group of teleuto- 

 spores ; 2, germinating teleutospore with two basidia ; 3, vegetative, 4, fructifying germinat- 

 ing basicliospore ; 5, a portion of a group of uredospores (u) and teleutospores (t) ; p, the germ- 

 pores ; 6, germinating uredospore. (1, 2, 3, 4, after Tcjlasxe ; 5, 6, after De Bary, from v. 

 Tavel ; 1 X 150, 2 X circa 230, 3, 4 X 3T0, 5 X 300, 6 X 390.) 



tion. The enveloping layer or peeidiitji of the secidia is formed of the peripheral 

 hyphse, which remain sterile. 



Uredospores and Eeeidiospores differ from the teleutospores only in their manner 

 of germinating vegetatively ; in the mode of their formation they are to be regarded 

 as chlamydospores, which serve a distinct biological purpose in the dissemination 

 of the Fungus. They have probably been evolved from teleutospores ; occasionally 

 transitional forms between teleutospores and uredospores are found. 



