250 ROMANCE OF LOW LIFE AMONGST PLANTS. 



fall upon a damp surface they in turn produce a germ- 

 tube, supposing- that the damp surface upon which 

 the promycelial spores fall should be a leaf of the 

 true host plant (in this case of Lapsand) the growing 

 point of the germ-tube enters the cuticle, and com- 

 mences to form a mycelium in the tissues ; meanwhile 

 all the contents of the original promycelial spore 

 passes down into the new mycelium, leaving the 

 spore-cell empty. 



The theory is, that from this mycelium, derived 

 from the germination of the promycelial spore, a 

 cluster of ALcidium, or cluster-cups, is produced, and 

 the cycle commences again, aecidiospores, uredospores 

 teleutospores, ad infinitjnn. From this we learn that 

 some of the "rust-fungi" pass through three forms or 

 stages, formerly regarded as three distinct fungi, 

 namely, yEcidiiim, livedo, and Piiccinia, a phenomenon 

 not only curious, but of immense importance in deal- 

 ing with them as diseases of plants. 



It is evident, from the foregoing details, that an 

 immense power of reproduction is given to these 

 minute plants. The secidiospores, by germination, 

 are able to reproduce themselves directly upon the 

 host plants, and thus, whatever their influence on 

 the subsequent uredospores, multiply the sources of 

 infection. The uredospores, possessing the power of 

 germination, can transfer the uredo to unaffected 

 leaves, and thus indefinitely extend the uredo form, 

 not only upon the same host plant, but to other host 

 plants of the same species, growing in proximity. 

 And finally the teleutospores, by remaining at rest 

 through the winter, provide for the initial infection 



