76 PHTLOGENT 



on the higher families would be expected to show the greatest 

 advance. This consideration alone is sufficient to determine 

 that Uredinopsis is like one of the primitive Uredinales and 

 that the genera Puccinia and Uromyces contain the highest 

 types. For Uredinopsis grows upon Ferns, and more than a 

 quarter of the Pucciniae live on the Composit.-e. 



Secondly a comparison of the spores of these two genera 

 and their respective allies suggests that the possession of a 

 single definite and well-formed germ-pore is a characteristic of 

 the latest forms, while the primitive ones had no germ-pores 

 at all, but protruded the germ-tube, as a conidium usually 

 does, at any convenient point or where the wall first gives way. 

 There is reason, from another point of view, to conclude that 

 germ-pores., when first existing, were numerous and indefinitely 

 scattered. A gradual reduction in their number and their 

 restriction to definite parts of the spore-wall occurred during 

 the course of evolution. The reeidio-teleutospore of Endo- 

 phyttum has no germ-pore; in the Pucciniaceae the secidio- 

 spores have usually several indistinct ones, the uredospores 

 have them fewer and more easily visible, and the teleutospores 

 have one or a small number, oftentimes very plainly marked. 



Amongst the other Fungi, the group which presents the 

 nearest approach to the Uredinales is that of the Ustilaginales, 

 which are also parasites ; their teleutospores (brandspores), in 

 the family Ustilaginaceae, germinate in a similar way, but with 

 less definiteness, by the formation of a basidium and basidio- 

 spores. It may be inferred that this particular feature is one 

 of the most deeply seated characters of both groups, and is 

 therefore inherited from their ancestors. 



Moreover, this feature is exhibited in the Uredinales by 

 cells which belong to the sporophytic generation, and after a 

 certain amount of growth the mycelium produced by the 

 basidiospores bears the two kinds of gametes. An exactly 

 similar course of events takes place in certain Algse, e.g. 

 Grijjithsia, where the sporophyte bears tetraspores which on 

 germination produce a thallus which bears gametes. It is true 

 that in the Red Alga? the tetraspores are more usually arranged 

 in tetrahedral fashion, but other modes also obtain, among them 



