British UrcdinecB and UstilaginecB. 



for. The vegetative mycelium of most of the Uredinese 

 is very similar, although the spores are very diverse. The 

 mycelium, being present in the appropriate host-plant, may 

 give origin to several different kinds of spores, according 

 to the nature of the Uredine under examination, each kind 

 of which was regarded by the older botanists as being a 

 distinct genus {yEcidium, Uredd). While it is true that 

 the relationship between the various spore-forms was 

 suspected as early as the beginning of the present century, 

 yet its actual demonstration has been accomplished only 

 within the last thirty years. From the investigations of 

 Tulasne and De Bary, we now know that each spore-form 

 has a life-history of its own, that they are often products 

 of the same mycelium grown among different environments, 

 and that they all arise from some antecedent spore-form. 

 The ultimate condition in which all the Uredineae are 

 encountered is the teleutospore, which, after a longer or 

 shorter period of quiescence, manifests its vitality by ger- 

 minating and producing a body — the promycelial spore. 

 The promycelial spore may then be regarded as the 

 beginning of the series of spore-forms of which the teleu- 

 tospore is the end. 



The actual number of spore-forms intervening between 

 the promycelial spore and the teleutospore is subject to 

 considerable variation in different species. 



1. The promycelial spore, after emitting a germ-tube, 

 which enters the tissues of its appropriate host-plant, may 

 give rise to a mycelium, which produces teleutospores 

 exactly similar to the teleutospore from which it originated 

 (Leptopuccinia, Micropuccinia). 



2. The promycelial spore in a second group of the 

 Uredinea;, in like manner, gives rise to a mycelium which 

 produces uredospores, and subsequently teleutospores 

 (Hemipuccinia). 



