106 INTRODUCTION TO THE STUDY OF FUNGI 



mostly to the phenomenon of conjugation, and resulting in the 

 production of zygospores. The polymorphic developments 

 cannot be described here, so that it must suffice to say that 

 the Mucors and the fish moulds (Saprolegniaceae), the rotting 

 moulds, such as the potato disease (Peronosporaceae), and some 

 other peculiar forms of Fungus structure, constitute this inter- 

 mediary group. 



What remains of the organisms generally grouped under 

 the designation of Fungi are rather outside families, the rela- 

 tionships of which are still somewhat uncertain. Here belongs 

 the Saccharomyceteae or yeast Fungi, although there is no room 

 for doubt that they are correctly united with Fungi ; but their 

 aquatic habit, low organisation, and imperfect fructification 

 justify their relegation to the lowest place. They are, doubt- 

 less, to a large extent, imperfect forms of some higher group. 

 Similarly the microbes, or bacterial organisms, the minute 

 Schizomyceteae, which in former times were mostly associated 

 with Algae, find a place in juxtaposition with the Saccharomy- 

 ceteae. The most aberrant group are the slime Fungi, or Myxo- 

 myceteae, which some few naturalists still claim for the animal 

 kingdom. In the early, or vegetative, stage they certainly 

 conduct themselves in a manner totally different from other 

 known Fungi, assuming amoeboid forms, and uniting in a Plas- 

 modium ; but in the final, or reproductive, stage they follow a 

 completely fungoid type, and produce spores which are not to 

 be distinguished from the spores of Fungi. Thus much is 

 sufficient to indicate the predominant features of the chief 

 groups of Fungi, and to demonstrate what are the kind of 

 plants which are associated within the limits of the short 

 definition first given of a Fungus. 



In the words of one author, who gave a definition of Fungi 

 thirty years ago, they " derive nourishment, by means of a 

 mycelium, from the matrix on which they grow " ; and this 

 furnishes a clue to their character and functions — i.e. as the 

 destructive agent in organic nature. That this is really the 

 case, a few illustrations will suffice to carry conviction. Of 

 the gill-bearing Fungi nearly 30 per cent grow upon decayed 

 wood ; the mycelium penetrates the tissues, disintegrates the 

 cells, and produces a condition which we call decay, but which 



