44 Bj'itish UredinecE and UstilaginecB. 



to be visible ; this is probably due to the elasticity of the 

 epidermal cell-wall. The germ-tube itself continues its 

 onward growth ; soon branching, it insinuates itself between 

 the cells of the host, where it gives rise to a mycelial 

 development, similar to that which arises from the aecidio- 

 spore or uredospore germ-tubes. 



With the Leptopuccinia and Lepturomyces, the germ- 

 tube of the promycelial spore does not bore its way through 

 the epidermal cells, but enters, as De Bary * first showed 

 with P. dianthi, through the stomata, or, as Rathay f points 

 out with P. malvacearum, it enters, like the germ-tube of 

 Tiibercinia trientalis, between the epidermal cells, and then 

 pierces laterally into the side of the adjacent cell. 



If the germination of the promycelial spores takes place 

 in water, and not upon their proper host-plant, the germ- 

 tubes sometimes become swollen at their extremities, so 

 as to form reserve spores in the same manner as has been 

 previously described with the uredospores (Plate III. 

 Fig. 24). 



The mycelium produced from a promycelial spore in 

 the tissues of its proper host-plant in due time gives rise 

 to a fresh spore-development. This spore-development, 

 however, varies in different cases. 



1. In certain species the mycelium produces spores 

 which are exact counterparts of the original teleutospores 

 (Micropuccinia). 



2. It may give rise to teleutospores similar in general 

 appearance as to its progenitors, but endowed with the 

 faculty of immediate germination (Leptopuccinia, etc.). 



3. It may give rise to a crop of uredospores, which may 



* De Bary, "Champ, paras.,'" A>in. Sc. Nat., 4"" ser. tome xx. p. 84 

 (reprint). 



t Rathay, " Ueber d. Eindringen. Puccinia Malvacearum," Verhandl. d. 

 Kk. Zool. bot. GiS., band xxxi. (iSSi), t. i. 



