70 J. W. REED OX UROMYCES PISI. 



alight on the Euphorbia leaves germinate, enter the tissues, and, 

 in course of time, produce the secidiospores. The secondary- 

 spores produced by the teleutospores germinate only on the 

 Euphorbia and not on the'pea, whereas the secidiospores formed on 

 the Euj)horbia germinate only on the pea. 



" Distribution. — Italy, Sicily, France, Switzerland, Austria, 

 Belgium, Germany, Bohemia, Finland, and Asiatic Siberia. It is 

 fortunately rare in Britain, as the Euphorbia is not a native. 

 The Euphorbia, however, is not uncommon as an ornamental 

 plant in cottage gardens. 



" To effect a cure for this disease, it is only necessary to 

 remove from the vicinity one of the two host-plants essential to 

 its existence." 



As just mentioned, the mycelium in the Euphorbia goes on 

 producing the eecidia as long as the host lives. It not only does 

 this, but, by the use of suitable reagents, such as caustic potash, 

 can be seen penetrating almost every part of the plant, descend- 

 ing mainly by its vessels. During the winter, when the Euphorbia 

 dies down, the mycelium hibernates in the rhizome. 



The life -history of Uromyces ^J^s^ exhibits the maximum 

 number of known spore relations, which is five ; one or more 

 being suppressed in some species. We have the pro-mycelial 

 spore, the sperm ogonium, the secidiospore, the uredospore, and the 

 teleutospore. 



The spermogonia are generally formed below the upper surface 

 of the leaf bearing the secidia, and are developed from the same 

 mycelium. Sometimes, however, they occur on the lower surface, 

 and in several of my sections they are shown thus in juxtaposition 

 with the secidia. These flask-like growths in the sub-cortical 

 tissue, with brushes of hau^-like filaments at their projecting 

 apices, pour out at maturity vast numbers of spermatia — 

 extremely minute bodies resembling spores — which have been 

 held by some to 'be the male sexual element. There seems, 

 however, to be a consensus of opinion, amongst fungologists, that 

 there is not sufl&cient warrant for this idea. The spermatia are 

 associated with a \dscid fluid ; and Dr. Cooke, in the fourth 

 edition of his " Kust, Smut, Mildew, and Mould," published in 

 1878, says that the largest examined up to that time were only 

 the o^jVo ^^ ^^^ ^^^^ ^^ length and the xooViro ^^ ^^ ^^^^^ ^ 



