^cidiospores. 2 7 



confounded with circumnutation bv some authors * but is 

 simply a hygrometric phenomenon. The distal extremity 

 of the germ-tube of an aecidiospore gains an entrance 

 into the tissues of the host-plant through one of the 

 stomata. This is effected by either the end of the germ- 

 tube or one of its principal branches insinuating itself into 

 the cleft (Plate II. Fig. 10). When an entrance has been 

 achieved, further development takes place in the air-spaces 

 below the stoma, by the branches of the germ-tube grow- 

 ing between the cells of the host-plant ; these soon develop 

 into a mycelium, which in due course produces the spore- 

 form proper to the species. 



The time which the aecidiospores retain their germi- 

 native faculty is stated by De Bary f to be some weeks. 

 From my observations, I should say it is rather a matter 

 of hours. Much depends, however, upon the temperature 

 and the amount of dryness to which the spores are ex- 

 posed. If they be placed in a very moist atmosphere, 

 they germinate at once ; if, on the contrary, in a perfectly 

 dry one, they almost as rapidly die. But if they be kept 

 slightly moist and cool,' they will remain uninjured for a 

 much longer time. I have, however, seldom found them 

 germinate after forty-eight hours, and then only a small 

 proportion will do so. It is only the mature spores at the 

 top of the cup, that have already separated themselves 

 from the spore-series, which will germinate. The process 

 begins within a i^w hours after they have been placed in 

 water. 



* Cooke, "Circumnutation in Fungi," Quekett Journal {i%%if)y vol. i. 2n(i 

 series, p. 309. 



+ De Bary, " Vergleich.," p. 369. 



