351 



schwellen dicklich an, werden vollsaftig und rothlich gefarbt und sind 

 unterseits wie mit Mehl iiberstreut, seltener." 



Sadebeck (86) and Fr. Thomas (97) have both made the same ob- 

 servation separately and independent of the other mycologists; both 

 describe the penetrating form on Vaccinium myrtillus; Sadebeck does 

 not give it a special name, Thomas indicates the circumscribed form 

 as "f. circumscripta" and the penetrating form as "f. ramicola", consi- 

 dering both to be climatic forms as he finds f. circumscripta in the 

 lowlands and f. ramicola high up in the mountains. 



Rostrup has often dealt rather thoroughly with the species of Exo- 

 basidium on Bicornes. He considered them (R 96 1, 96 o ^^^, 02 a, 04 a) 

 a single species differentiated into many formae speciales. The pene- 

 trating form on Oxycoccus palustris he has, however, described as 

 an autonomous species, viz. Exobasidium oxycocci, and in some other 

 places he draws attention to the fact that Exobasidium from Green- 

 land (i. e. Exobasidium vaccinii uliginosi) has much larger spores, 

 viz: 16—18 ^l X 8—9 ¥■, than the Danish forms. 



Boudier (1894) has described the penetrating form on Vaccinium 

 uliginosum as Exobasidium vaccinii uliginosi; later on (96) Lagerheim 

 gave a more thorough description and delineation of the same. 



As long as the necessary cultivating experiments have not been 

 made I shall prefer to unite all the circumscribed forms in the single 

 species: Exobas. vaccinii and to consider Exobas. arctostaphyli, Exobas. 

 oxycocci, Exobas. myrtilli, Exobas. Karstenii and Exob. vaccinii uligi- 

 nosi as autonomous species, the latter has not been found in Den- 

 mark, it is common in Greenland and Lapland on Vaccinium uligi- 

 nosum, Vacc. vitis idaea and Cassiope tetragona. 



1637. Exobasidium vaccinii (Fuckel) Woronin, Syll. VI "", Syn: 

 Fusidium vaccinii Fuckel 61 ^^'' c. icon., Exobas. ledi Karsten in Thiim. 

 Mycot. no 1506, Syll. VI ^^' 



It not only attacks the leaves, but occasionally may cause quite 

 short and thick witches'-brooms on the end of young twigs of Vacci- 

 nium vitis idaea. The form on Rhododendron — Exobasidium rhodo- 

 dendri Cramer, Syll. VI ^^* — is surely no independent species. A. 

 Bruun has observed that Rhododendron hirsutum which had been 

 growing in a hot-house for many years without being attacked was 

 one year infected, possibly from Vaccinium vitis idaea (see R 95 a ^''^). 

 Nor is the form on Azalea — called Exobasidium azaleae Peck or 

 Exob. discoideum Elhs &. var. Horvathianum Thiimen — an auto- 

 nomous species (see Naumann 1910). 



Common. July— September on Vaccinium vitis idaea, Vaccinium uliginosum 

 Oxycoccus palusMs. Rhododendron hirsutum. S. Hellebaek (Bergesen), Landbo- 



