ABSTRACT
In classifying composite organisms like lichens, in the practically necessary task of constructing some sort of system of 'natural communities' of plants and/or animals, in dealing with things like pollen grains and various types of micro-fossils, also in the practically important 'fungi imperfecti', special difficulties are liable to be encountered. In this chapter some of them are briefly considered, beginning with the fungi imperfecti. The major division of the fungi are defined in relation to the characters of the spore-bearing stage, whose production normally involves some form of sexual fusion. The classificatory value of pollen grains is well reviewed in a recent article by Erdtmann. His assertion that pollen grains 'appear as an alter ego of the parent plants, reflecting the "macro-individuals", the trees, shrubs, herbs, etc., that produced them' may convey a somewhat misleading impression.
