116 MicEoscopic ruwai. 



The under surface of the leaves of the white 

 Dutch clover are often sprinkled with black spots, 

 which are nearly round and very numerous. These 

 are so many clusters of fungi belonging to a 

 different section, in which the threads are the 

 important feature. But another parasite is also 

 found on leaves of the same plant, in which the 

 pustules are far less numerous and regular, and 

 are often found on the petiole as well as the leaf, 

 distorting them and twisting them in various direc- 

 tions (plate Vn. fig. 154). This is the clover rust 

 {Uromyces apiculata, Lev.), which is a parasite on 

 numerous plants, being found also on the great 

 water-dock and other kinds of dock. The spores 

 are ovoid and brown, with a short peduncle (plate 

 VTI. fig. 155). A very beautiful species occurs on 

 the leaves of the ladies-mantle [Alchemilla), but 

 hitherto we have not found it to be at all 

 common. 



It can scarcely be too great an assumption to 

 suppose that every one is acquainted with the goat- 

 willow {Salix ca/prea), or that every schoolboy 

 knows the birch {Betula alba). It may be pro- 

 ceeding a step too far to aflfcm that all who know 

 these trees well enough to distinguish the one from 

 the other, wiU have observed the under surfaces of 

 the leaves of both sprinkled with a golden dust, 

 during the summer months, and which are the 

 spores of a parasitic fungus. So common is this 

 orange-coloared powder on leaves of the trees 



