6 FCNGOID PESTS OF CULTIVATED PLANTS. 



spores, into which some of the contents of the old spore pass, and these 

 smaller bodies are eligible for the production of mycelium, which is pre- 

 pared to find an entrance into the leaf of some young and new host plant, 

 and producing infection commence the cycle over again (fig. 2). Thus, 

 then, we have in order of succession spermogonia, aecidiospores, uredo- 

 spores, and teleutospores, each of the three latter capable of producing 

 secondary spores, but the last of all producing the promycelial spores 

 which are the medium of reinfection, from the complete and perfect 

 condition of the Puccinia. 



It may be mentioned, in passing, that the life-history in the genus 

 Uromyces, where the teleutospores are only one-celled, is precisely 

 similar. 



But all these stages are not always to be found associated together. 

 The chain is not always perfect. In some cases the JEtidium only is 



FIG. 2. TELEUTOSPORE GERMINATING. 



known, with or without spermogonia ; or in other cases only the uredo- 

 spores are known ; or in certain cases only the teleutospores. In each 

 of these instances the fungi are regarded as imperfect, or, at least, as 

 imperfectly known Uredines. 



Besides these cases, in which aecidiospores, uredospores, and teleuto- 

 spores are produced on the same species of host-plant, there is another 

 group which those w r ho have implicit faith in heteroacism contend 

 produce the aecidiospores with spermogonia on one species of plant, and 

 the uredospores and teleutospores on another and quite different species 

 of host-plant. Let each te persuaded in his own mind, as it will serve 

 no good purpose to enter upon discussion here. 



There is another group in which only the spermogonia, uredospores, 

 and teleutospores are known, and these all occur on the same host-plant. 

 Here the aecidiospores are absent. 



In a fourth group only the aecidiospores and teleutospores are known, 

 and these occur upon the same species of host-plant. The uredospores 

 are wanting or do not produce pustules of their own. 



In the fifth group teleutospores only are known, so that both aecidio- 

 spores and uredospores are absent, and the teleutospores only germinate 

 after a period of rest. In another subsection only teleutospores are 

 found, but they germinate at once on arriving at maturity, without an 



