FlNOOID PESTS OF CULTIVATED PLANTS. 



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

 smaller hodies arc 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, recidiospores, 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 Puecinia. 



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 JEcidium 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 ITredines. 



Besides these cases, in which a?cidiospores, uredospores, and teleuto- 

 Bpores arc produced on the same species of host-plant, there is another 

 group which those who have implicit faith in hetenecism 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 lo persuaded in his own mind, as it will servo 

 HO good purpose to cuter 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 .i-eidiospores are absent. 



In ;i fourth group only the ;ecidiospores 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 iecidio- 



pores and uredospores are absent, and the teleutospores only germinate 



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



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



