” Saccharomyces”, according to the book is the most common strain of yeast used to ferment beer. Their are two stains seemly – saccharomyces uvarum (originally carlbergensis, which has a familiar sound to it.) and saccharomyses cerevisae, the former is bottom fermenting while the latter ferments on top at slightly warmer temperatures producing what we call ale. This is how we ferment our beers, all of whom are ales regardless of their colour. I believe at one time beer was described as being determined by the fact that hops are added so ale would have had plants and herbs for flavouring. I note in todays world of drinking the common perception is that ale is red, not so seemly. A lovely analogy mentioned, is that both yeasts are members of the same family but have different table manners, there is a certain allusion to tolerance here!