EXOBASIDIUM. 



425 



from each a spindle-shaped spore is abjointed (Fig. 257). The 

 basidiospores divide in water by formation of cross-septa, and 

 a germ-tube arises from each terminal cell. On a young leaf 

 of Vaccinium the germ-tube 

 penetrates and gives rise to 

 a mycelium (Fig. 258); on 

 other substrata the germ-tube 

 sprouts into several very fine 

 sterigmata, from the extremi- 

 ties of which a series of couidia 

 are abjointed ; the conidia 

 may give off secondary coni- 

 dia, perhaps also tertiary. In 

 nutritive solution, Brefeld ob- 

 tained an increased number of 

 germ-tubes and a continuous 

 production of conidia ; in air, 

 conidia were produced on conidia, but inside the solution the 

 conidia gave off hyphae from which new conidia arose. 



Fig. •IbT.—Exohasidium vaccinii. The basidial 

 ayer Is shown developing from the intercellular 

 nycelium of the shoots. (After Woronin.) 



^f^ 



Fio. 258. — Exobasidium vaccinii. Germinating basidiospores. The septate spores 

 have given off germ-tubes which penetrate into the cowberry leaves, either by 

 stomata or through the epidermis. The lowest spore is forming conidia. (After 

 Woronin.) 



This Exobasiclium is very common on the cowberry ( Vaccinium 

 Vitis-Idaca)} It occurs less frequently on the bilberry {Vac- 



' Several American Ericaceae are given as host-plant.s in the " Host-hidex." 



