72 INTRODUCTION TO THE STUDY OF FUNGI 



First generation Baestelia, second generation Gymnosporangium, 

 third generation Baestelia, fourth generation Gymnosporangium, 

 and so on alternately, constituting an alternation of generations. 

 Technically, there is but one species appearing under two 

 forms, and the two names represent two conditions of the 

 same Fungus. 



Another illustration may be found detailed in a succeeding 

 chapter, in which another Uredine is traced through the 

 Aecidium-form, the Uredo-form, and the Puccinia-form, revert- 

 ing to the Aecidium-form in the fourth generation. It will be 

 observed that alternation of generations differs materially from 

 what we have designated dichocarpism, because in the former 

 a single generation produces but one form, and the second 

 generation proceeds directly from the germination of the 

 first, and consequently upon a new mycelium. In the 

 latter, dichocarpism, both forms of fruit are produced from the 

 same mycelium, and belong to one and the same generation. 

 "We have also seen that the number of forms which are possible 

 to a single species are not confined necessarily to two, but may 

 extend to three or four, whilst the principle remains the same. 

 Hence we conclude that the same species of Fungus is capable 

 of producing, on the basis of its own vegetative system, two or 

 more forms of fruit, one of which, but not both, may -be the 

 result of sexual fecundation. 



