ENDOPHYLLUM SEMPERVIVI 53 



Within these secidia the aecidiospores are produced ; these 

 will only infect the Juniper, on which they begin the 

 cycle again. 



For all these species of Gymnosporangium the only remedy 

 is to remove and burn the diseased Juniper, if it can be found ; 

 if it may not be destroyed, at least the affected branches should 

 be cut off, and the wounds dressed with Stockholm tar. It is 

 of no use to spray or otherwise treat the Hawthorn or Pear. 

 In them the disease is purely local ; it comes to an end when 

 the summer ends, and will not recur next year unless fresh 

 infection is conveyed from the Juniper. The harm done to 

 them is confined to the loss of the foliage which naturally 

 weakens the tree to some extent. 



Endophyllum Sempervivi. 



The Houseleek Rust. 



This parasite attacks the common Houseleek and numerous 

 other species of Sempervivum. It differs from nearly all the 

 other Uredinales in having only spermatia and aecidiospores, 

 the latter functioning also as teleutospores and producing basi- 

 diospores. This fungus has been thoroughly investigated by 

 Hoffmann (1911) from whom the following account has been 

 derived. 



The aecidiospores mature on the leaves in April and May ; 

 they have no visible germ-pores. They germinate at once, 

 while still in the secidium ; the germ-tube forces its way out 

 at some point of the circumference of the spore and elongates 

 to form the four-celled basidium. Each basidium produces four 

 basidiospores on long sterigmata; occasionally more are pro- 

 duced — Hoffmann observed as many as eight on one basidium. 

 The basidiospores may be blown on to the leaf of a Houseleek 

 where they germinate at once and bore through the cuticle ; 

 they form a holdfast (somewhat as a uredospore does) below 

 the outer wall and penetrate into the epidermal cell (see Fig. 17). 

 The mycelium then branches, passes through the intercellular 



