372 



UREDINEAE. 



influences young cells attacked by it during their period of 

 growth, whereas cells already in the adult condition remain 

 unaffected. 



Inside the diseased shoots a well-developed mycelium will 

 be found between the epidermal cells, and nourished by haustoria. 



FIG. 203. Calyptoxpora Gotppcrtiana. Section through epidermis and cortical 

 parenchyma of a diseased shoot of Vaccinium. The mycelium is intercellular, but 

 swollen branches penetrate the cell-walls and become sac-like haustoria. The 

 hyphae under the epidermis become considerably swollen, and give off into the 

 cells either haustoria (b) or the sac-like processes (c, c), which become the mother- 

 cells of the teleutospores. < 420. (After R. Hartig.) 



The spores originate from processes of the mycelial hyphae, 

 which bore their way into the epidermal cells, and swell up 

 inside to form spherical sacs. The cells thus entered turn 

 brown, and are filled up by four to eight cells produced from 

 the sac-like processes of the mycelium (Fig. 203). From each 

 cell of this kind a four-celled teleutospore is formed and hiber- 

 nates in situ. In spring the teleutospores emit a process through 

 the outer wall of the epidermal cell, and this, after division 

 by cross-septa into four cells, becomes a promycelium with short 

 sterigmata, from each of which a single sporidium is abjointed 

 (Fig. 204). The sporidia germinate, as Hartig proved, about the 

 middle of May, on young needles of silver fir (Abies pecfinnfn). 

 By the middle of June the mycelium is distributed through 

 the intercellular spaces, and forms aecidia with long white sac- 

 like peridia on the under surface of the leaf (Figs. 205, 206) 

 The aecidiospores escape on rupture of the peridiimi and the 



