GERMINATION OF vECIDIOSPORES 7 



tapping are mature enough to germinate, and even they, owing 

 to their thin walls, may lose this power in a few days according 

 to circumstances. Especially can they be killed by rapid 



Fig. 5. P. Caricis. a, three cells of the peridium, on Nettle ; b, a cell in 

 optical section; c, the same in surface-view ; d, two acidiospores. x 600. 



drying. Instances are known, however, where some of them, 

 kept in a cool place, retained their capacity for germination 

 about seventy days, though most of them were dead after 

 eighty days. 



Each spore has a number of germ-pores ; in Puccinia Caricis 

 the number is about five or six ; in other species of Uredinales 

 the number varies from two to eight. 

 These pores, which are scarcely visible 

 until germination begins, are thin places 

 in the inner layers of the outer wall, the 

 whole cell bearing a close resemblance to 

 many kinds of pollen-grains (microspores). 

 (Fig. 6.) 



It is worthy of notice that in the 

 spores of Endophyllum, and others of the 

 less advanced type, there are no real germ- 

 pores ; the germ-tube merely forces its 

 way out at the first place that gives way. 

 From this state of things there is a gradual 

 transition from numerous to few germ-pores ; in the highest 

 types of all (Uromyces and Puccinia teleutospores), each cell 

 has one and only one well-defined germ-pore. 



Fig. 6. vEcidiospore of 

 P. Caricis, germinating 

 in water, x 180. 



