GALLS CAUSED BY FUNGI 
119 
the place of bracts in pistillate flowers of the Common 
Alder. These peculiar galls result from the presence of 
Exoascus alnitorquus ; they are sometimes 30 mm. long, and 
as many as ten small ones may occur on a single catkin. 
They may be found from June to October, but are rare 
in Britain. Alder trees abound at Haslemere, but I have 
never succeeded in finding the galls in this district. 
In the latter part of May and throughout June Nettles 
afflicted with the aecidial stage of Puccinia caricis are fre¬ 
quently met with. The gall which arises is very noticeable ; 
the condition is well shown in Plate XVI., Fig. 2. The 
stem becomes greatly swollen and bent; immersed in the 
swollen tissue are the bodies (pseudoperidia) containing the 
Fig. 33 — Female Catkins of Alnus glutinosa, the Upper 
galled by Exoascus alnitorquus. 1/2. 
orange-yellow aecidiospores. The fungus also fruits on the 
leaves, forming yellow spots. It is heteroecious, and the 
aecidial stage is known under the name of Aecidium urticae. 
The aecidiospores are carried to various Sedges, on which 
the teleutospores are produced from July to April. 
On the same plate (Fig. 3) may be seen grass stems 
attacked by the “ Reed Mace ” fungus, Epichloe typhina. 
Afflicted plants do not flower, and growth is seldom pro¬ 
longed above the galled part, which is usually the upper leaf 
sheath. Upon its first appearance on the stem the fungus 
is a thin whitish crust ; it becomes yellow later, and is then 
studded with the mouths of the perithecia immersed in the 
