WITCHES’ BESOMS 
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abundant in the South of England. Diseased leaves often 
fall before midsummer, and should be carefully collected 
and burned. Pruning, as in the preceding species, checks 
the spread of the disease. 
Fig. 6 . Ascomyces alnitorquus produces blisters on the upper 
surface of the leaves of the common alder (Alnus glutinosa ), 
and causes remarkable gall-like productions on the female 
inflorescence. Ascomyces tuvgidus gives rise to the “ witches’ 
besoms ” so commonly seen on birch, and particularly 
noticeable in winter. The asci are formed on the under 
surface of the leaves, which become discoloured, and appear 
as if dusted with a greyish hoariness. 
Amongst other parasitic Ascomycetes may be mentioned 
the members of the genus Sclerotinia. Many of these 
are well-known garden pests. S. sclerotionmi (Plate V.) 
attacks the potato, chrysanthemum, cucumber, etc. It first 
appears above ground as a delicate white mould, encircling 
the stem of the attacked plant. The mycelium spreads up 
into the centre of the stem, in which the black sclerotia 
may be easily detected in their season. S. tuberosa attacks 
anemones, wild and cultivated. The sclerotium is attached 
to the anemone root. The long stem of the ascophore is 
buried in the ground, hence the fungus appears like a sessile 
Peziza. Other species of Sclerotinia attack peonies, tulips, 
and snowdrops. Peziza vesiculosa (Plate XLVII.) is said to 
attack species of Balsaminia, Hyacinthus, etc., in gardens. 
The ascophores should be carefully collected and burnt. 
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