UREDINALES 593 



shifting of the gametophyte from Rosaceae to conifers. Their teliospores 

 usually resemble those of Phragmidium. 



The remaining mixed genera which contain both autoecious and 

 heteroecious species, particularly Uromyces and Puccinia, in contrast 

 to the Coleosporiaceae, Melampsoraceae and Cronartiaceae, are distin- 

 guished in their change of host by a great stability in their sporophyte 

 which chiefly inhabits the Glumiflorae, while their gametophytes have 

 been spread to more than 50 families of angiosperms and again have 

 become largely specialized to specific hosts. From these species, by a 

 reduction of the life cycles, have arisen numerous micro- and endo- forms 

 (E. Fischer, 1904, 1910; Dietel, 1918). In the micro- forms, meiosis 

 came about in the long-cycled species as a result of a simplification of the 

 life cycle where all spore forms up to the teliospore and eventually the 

 pycnia were suppressed. In other cases there must have taken place a 

 shifting of place of teliospore formation; thus the telia discussed on page 

 568 of Puccinia Fergussoni on Viola do not coincide with the structure 

 of telia but with the aecia of the corresponding eu- form, Puccinia Violae, 

 and in Uromyces scutellatus, U. laevis and U. alpestris on Euphorbia 

 (mentioned on p. 568). Altogether one obtains the impression that the 

 sorus was originally developed as an aecium, later became indefinite and 

 was merged with the telia. These forms appear chiefly in tropical, alpine 

 and polar regions. 



The development in the endo- forms has proceeded a step further; 

 here also caryogamy has been advanced into the aecium, occurring in 

 aeciospores rather than teliospores. While in the micro- form, Uromyces 

 alpestris, teliospores are formed within the sori, originally considered to 

 be aecia, where caryogamy takes place, in the endo- form, Endophyllum 

 Euphorbiae-silvaticae on Euphorbia, the original tendency of the sori to 

 form aeciospores preponderates and caryogamy takes place there. 

 According to this conception the endo- forms are the end members of a 

 series of developments which, by shifting of teliospore formation in 

 certain micro- forms, became introduced into the aecium. Both Endo- 

 phyllum (with aecidia) and Kunkelia (with caeomata) may thus be con- 

 sidered, not as natural monophyletic genera, but as biological groups 

 similar to the brachy- and hemi- groups. As an initial impulse for these 

 modifications, we may consider a migration of the mother species into 

 warmer regions. Thus the ancestral form on Rubus, Gymnoconia 

 Peckiana, is found in the colder regions of North America, while its 

 apparent derivative, the endo- form Kunkelia nitens, also on Rubus, is 

 found in the warmer regions of the South and West. Besides, the number 

 of endo- forms known from the tropics is continually increasing. In con- 

 nection with this degeneration have again arisen forms in the Pucciniaceae 

 quite similar to the primitive forms and consequently were considered 

 primitive by many authors (E. Fischer, 1912; Groves, 1913). 



