44 Smuts in their Relation to Rusts. 



the older and more mature being on the outside, and thev are often contained 

 in a special receptacle formed by several layers of sterile cells. So striking 

 is the resemblance that Brefeld asserts that if the characters of the two 

 genera were united in one form there would be almost complete agreement 

 with the aecidia of the rusts, and he considers it not improbable that such 

 forms may yet be discovered. In such a case the smuts might reasonably 

 be regarded as the progenitors of the rusts, the primary forms from which 

 they were derived. 



If we sum up the principal resemblances and differences between the 

 smuts and the rusts, it is found that they agree in the following : — 



1. They are all parasites. 



2. They produce a promycelium bearing c0]iidia. 



3. A peridium is sometimes present, and spores are produced in a 



radiating manner resembling an aecidium. 



And they differ : — 



1. In the promyceKum producing a variable number of conidia. 



2. In the promycehum of some species growing and branching in a 



vegetative manner without the formation of conidia. 



3. In the mode of production of spores, which are formed in the 



interior of the hyphae and not pinched off at their apex. 



4. In the production of one spore form, and not a variety. 



5. In the absence of a true sexual process. 



