EXOBASIDIUM. 427 



Ex. rhododendri Cram. (Britain and U.S. America). This 

 causes gall-like outgrowths on the leaves of the Alpine- rose 

 (Bhododendron femtgineum and Hh. hirsutum). The swellings 

 may be small and fairly hard, or, attaining the size of cherries 

 or plums, they may be soft and spongy so that they shrivel 

 up soon after the twig is cut; in colour they are yellowish- 

 white, but on the side exposed to sunlight become rose-red ; 

 the ^xobasidium-galh may even be formed on the small rolled- 

 up leaves caused by attacks of mites. 



Ex. Peckii Hals.^ [This species occurs in the flowers of 

 Andromeda Mariana in the United States. It is coniined 

 almost entirely to the inflorescences, and causes considerable 

 distortion. The bell-shaped corollas are replaced by ones quite 

 polypetalous, and the ovary becomes raised above the re- 

 ceptacle.] (Edit.) 



The following five species have been recorded on Ericaceae 

 in America : 



Ex. azaleae Peck. On Rhododendron nudijlonim. 



Ex. discoideum Ellis. On Rhododendron visoosmn. 



Ex. decolorans Hark. On Rhododendron viscosum and R. occidentide. 



Ex. arctosta.phyli Hark. On Arctostaphylos pungens. 



Ex. cassandrae Peck. On Caasandra calyculata. 



Other species to be mentioned are : 



Exobasidium ledi Karst. On Ledum palustre. 



Ex. Warmingii Rostr. (U.S. America). This occurs on Saadfraga Aizoon, 

 8. hryoides, S. aspera, etc. ; it causes marked hypertrophy of the leaves, and in 

 this way, as well as by its many smaller spores, is distinguished from : 



Ex. Schinzianum Magn. On the leaves of Saadfraga rotundifoUa, causing 

 whitish spots which soon become brown and die. 



Ex. symploci Ellis. On Symplocus tinctoria in North America. 



Ex. graminicolum Bres. On leaves of various grasses, e.g. Bronms, 

 Arrhenatherum, etc. 



Ex. lauri Geyl.^ is said to produce branched outgrowths of over three 

 feet in length on Laurus nohilis and L. canariensis in the Canary Islands. 



Urobasidium rosiratum Ghgn. occurs on the " witches' broom," out- 

 growths caused by Taphrina cornu-cervi Ghgn. on Aspidium aristatum 

 in India. 



iHalsted, Bulletin of the Torrey Club, xx., 189.S, p. 437. 

 ^Geyler, Botan. Zeitung, 1874, p. 322, PI. VII. 



