DI-MORPHISM. 37 



Sjphceria common to various plants ; these moulds 

 having been hitherto regarded as fungi perfect in 

 themselves. 



In the Uredines, to which much of this volume 

 is devoted, the genera known as Lecythea and 

 Trichobasis are by some mycologists excluded 

 altogether, as containing only species which are 

 mere forms of more highly- developed uredines, 

 such as Puccinidj Aregma, and others. On the 

 other hand, they are retained by those who possess 

 a lingering doubt whether both forms may not be 

 distinct, though developed from the same pustule. 

 As the two forms are distinct in appearance, it will 

 better answer our present purpose to treat them 

 separately, notwithstanding the belief that, in a 

 scientific point of view, the evidence is all in favour 

 of their union. 



In fungi of this kind the mycelium, or delicate 

 root-like threads, consists of thin filaments, which 

 are spread through all parts of the plant occupied 

 by the parasite, traversing the intercellular pas- 

 sages, but rarely perforating and entering the cells. 

 This compacted and interwoven mycelium forms a 

 kind of cushion beneath each pustule, on which the 

 fruits of the parasite rest. By the increase of this 

 cushion and the swelling of the fruit, the epidermis 

 which covers them is distended," and ultimately 

 ruptured, so that, when ripened, the spores escape. 

 It must be remembered that the fruit is of from 

 two to four kinds. Small bodies, called sjjennatia, 



