350 



90" 6. tab. 1, Slimet Hornsvamp (R 98 q=^^ c. icon.), Klaebrig Kelle- 

 svamp (H. 37 «==). 



Very common on stumps of coniferae July— October. 



Exobasidiineae. 



Exobasidium. 



It is very difficult to decide whether all the species of Exobasidium 

 proposed are autonomous species or not. We are badly in want of 

 cultivating experiments to decide whether a number of the so-called 

 species are only biological forms. Richards alone (96) has made a few 

 experiments to this effect in 1894. 



The systematic division of the species of Exobasidium parasitical 

 on Bicornes is rather complicated and has caused a great many mis- 

 understandings, even in the latest systematical manuals (for instance 

 E. &. P. 00) the facts are by no means cleared up. So I shall be obliged 

 to deal a little more thoroughly with the classification of this group 

 of fungi. 



There are three different, morphologically well separated types of 

 Exobasidium on Bicornes in this country and in the neighbouring ones. 



The first type which I shall call the circumscribed one has its recep- 

 tacle on limited spots on the leaves forming irregular gall-like bodies; 

 the basidia are crowded with four spore-bearing sterigmata; the spo- 

 res are small: 5—8 H^ X 1— 2 K 



The second type which I shall call the penetrating one penetrates 

 the whole of the host-plant or single branches with its mycelium 

 causing hypertrophical deformations on them and producing witches- 

 brooms. The basidia bear only two sterigmata and the spores are 

 large: 25-32 l^ X 8-12 l^. 



The third type occupies in many respects, an intermediate position 

 between the above two types, and it only occurs on Arctostaphylos. 



No doubt Wilhelm Siegmund was the first to notice the two types 

 which I call the circumscribed and the penetrating one. His descrip- 

 tions seem to be quite unheeded by all later mycologists so they are 

 quoted here. He writes (79^^): 



"Exobasidium vaccinii Woronin. An lebenden Blattern der Preisel- 

 beere warzenformige fleischige verdickte Auswiichse, welche unterseits 

 wie mit Mehl iiberstreut und oben schon roth gefarbt sind, auch am 

 Vaccinium uliginosum. 



Exobasidium myrtilli. Die Zweige und Blatter der Heidelbeere 



