The grass family is remarkable both for its naturalness and for its distinctness from neighbouring groups. Though other families have sometimes been included with it in the order Glumales or Glumiflorae, the most recent tendency is to treat it as a group apart, and to regard the resemblances which it shows, for instance, to the Sedge family (Cyperaceae), as indicating parallel development rather than affinity. If this view be accepted, I should like to suggest that the established word Gramineae might be retained for the order; the name Graminaceae could then perhaps be used for the only family included in this order.

Within the group itself, classification presents special difficulties; the subdivisions have even been described as “complétement artificielles”. The species are very numerous—they are estimated as 8000, or even more, grouped in about 550 genera—and their structural characteristics do not lend themselves to any obvious classificatory scheme. Indeed, as Kunth wrote, more than a hundred years ago, “dans les families eminemment naturelles, comme celles des Graminées, … on ne trouve que très-peu de caractères … qui puissent servir à distinguer les genres, et le plus souvent ces caractéres sont aussi vagues que minutieux”. In classifying the grasses, botanists have thus been obliged to rely, even more than usual, upon that intuitive faculty for detecting affinities, which can be cultivated to a high pitch by “la grande habitude de voir”. There is nothing magical about this faculty; it is the subconscious result of long labour acting upon an instinctive interest.