With such a wide range of environmental resources and no less than half of the national territory under the plough during the July Monarchy striking spatial differences are to be expected in the distribution and association of the twelve 'crops' that made up the arable realm. Each crop responded to ecological and economic factors to display its own discrete pattern of production. Physical parameters were obviously of great importance in creating these patterns but for four main reasons they may be discussed in only a cursory fashion. First, contemporary literature made little mention of the precise strains that were grown and hence one remains largely ignorant of the detail of tolerance limits. Second, the complexity of environmental resources defies adequate synthesis for some kind of index to be applied meaningfully to production figures for each arrondissement. Third, the cultural context of crop production was poorly recorded. Standardised information on man/land relationships in the 1830s simply does not exist and it is impossible to determine with any precision how many people worked the land, the types of tenure under which they operated or the size of holdings that they farmed. Hence the characteristics and intensity of farming systems may be indicated in only a partial way. Fourth, the degree of openness of particular pays to market forces remains largely a matter of conjecture, although simple location, information on land and water routes, and differences in commodity prices provide some clues.