The biochemical capabilities summarised in Chapter 3 are used in a variety of ways during morphogenetic processes in fungi. In this chapter I will describe and discuss some of these. Throughout this account from now on my emphasis will be on finding general principles to weave into an overall model of fungal morphogenesis. Experimental observations, of course, deal with specific cases under particular conditions. I will describe some of these specific cases but, as I cannot describe them all, I have selected examples which seem to me to illustrate particular points which need to be included in any overall picture of morphogenesis. Other examples can be found in the literature and I will make reference to some of them. Furthermore, by attempting to generalise from the few cases I can illustrate, I will be relying on making inductive inferences, some of which will, inevitably, be more reliable than others. It is necessary to take the risk of being wrong in order to get some view of the overall picture.

The variety of data in the literature indicates that the major events in the growth and differentiation of a mycelium are essentially as follows. During growth of the vegetative hyphae a large proportion of the nutrients adsorbed from the substratum is stored. Different organisms use the different storage compounds (polysaccharide, protein, oils and fats and polyphosphates) to different extents.