GERMINATION OF BASIDIOSPORES 15 



If one of these easily detached basidiospores or conidia is 

 conveyed to the surface of a leaf or young stem of Nettle, its 

 germ-tube bores through the cuticle 

 and enters the tissues (Fig. 17), 

 where it ramifies and forms a my- 

 celium. The teleutospore is large 

 and heavy, and firmly attached to 

 its spore-bed on the leaf of Carex ; 

 the basidiospores enable its con- 

 tents to be transferred easily to Fi §- 17 \ Endophyllum Sem- 



J pervwi. (Terminating basi- 



the surface on which alone they diospores (after Hoffmann) ; 



i i c c j-i j.1- "D j. s, the spore; v, the germ- 



are capable of further growth. But v ' esicle; mlder t £ e cuti * le of 



their wall is thin and they can live th e epidermis ; a,b, c, show 

 , n i , • the passage of the spore- 



only for a short time ; they contain contents into the vesicle. 



but little food-supply and could not x about 20 °- 

 form a long germ-tube. That is the reason why their germ- 

 tubes do not, like those of the other spores, search for a stoma, 

 but enter by the quickest means. Nevertheless they can 

 abnormally enter by a stoma ; De Bary records such a case in 

 his account of P. Dianthi (see Fig. 24). 



The germination of the teleutospores of P. Caricis takes 

 place about the second week in April, and on the mycelium 

 produced by the basidiospores in the nettle there arise, in 

 about a fortnight, first spermogones and then secidia like those 

 with which we started. But the mycelium arising from the 

 basidiospores does not always proceed immediately to spore- 

 production. In some species, e.g. Endophyllum Sempervivi, it 

 hibernates in the growing point of the shoot, or in the leaves 

 if they are evergreen, as in Puccinia Buxi, or in the steins or 

 branches in the case of some that live on shrubs or trees, as in 

 Cronartium ribicola. 



Rather more than a twelfth of the species of Uredinales are 

 now known to be heteroecious. This mode of life may be 

 regarded partly as a device by which the parasite tides over 

 the time during which one of the host-plants is not available. 

 The leaves of the Nettle are delicate and soon perish in the 

 autumn ; those of the Sedge persist throughout the winter. 

 The power of heteroecism increases the ability of the fungus to 



