166 



TRANSACTIONS OF THE 



[Sess. 



is not of generic rank, and makes it a section of the genus 

 Puccinia. The forms placed in this section are nearly all 

 American, and none of the British species hitherto recorded 

 are included in it. 



1. Uiedospore with ijcdicel. '2 and 3. Uredospores in oj^tical section 

 showing germ -pores. 4. Germinating uredospore. 5. Teleutospore showing 

 germ-pores in surface view. 6 and 7. Teleutos])ores showing variation in 

 point of attachment of pedicel. 8. Teleutos]>ore in optical section showing 

 germ-pores ; one jjore in the lower cell is at a slightly lower level. 9 and 10. 

 Germinating tcleutospores. 



The method of dehiscence of the spores in this rust is of 

 interest. As already described, the uredospores are dis- 

 tinctly articulated to their pedicels and become easily de- 

 tached from them. The sorus has a powdery appearance, 

 due to the large number of detached uredospores lying on its 

 surface, the pedicels of which make up the inner portion of 

 the compact fructification. The few telcutospores in each 

 sorus project beyond the uredospore layer on accoimt of their 

 long pedicels. Dietel ^ has pointed out that in this and several 

 other rusts the base of the teleutospore pedicel rapidly absorbs 

 water when placed in it, and, in consequence, swells and 



* Uber Quellungserscheinungen an den Toloutosporenstielen von 

 Uredineen, .Jahrb. wiss. Bot., xxvi, 1894, p. 49. 



