Previous directives of INAO make conditional allowances according to the complex laws of 1927 and 1929, and plantings made before 1938. Before the 2010 regulations, the complete list of the actual and theoretical varieties also included and Pinot Rosé. The Gamay vines of the region were scheduled to be uprooted by 1942, but due to World War II, this was postponed until 1962, and this variety is no longer allowed in Champagne. The dark-skinned Pinot noir and Pinot meunier give the wine its length and backbone. They are predominantly grown in two areas – the Montagne de Reims and the Vallée de la Marne. The Montagne de Reims run east-west to the south of Reims, in northern Champagne. They are notable for north-facing chalky slopes that derive heat from the warm winds rising from the valleys below. The River Marne runs west–east through Champagne, south of the Montagne de Reims. The Vallée de la Marne contains south-facing chalky slopes. Chardonnay gives the wine its acidity and biscuit flavour. Most Chardonnay is grown in a north–south-running strip to the south of Épernay, called the , including the villages of Avize, Oger and . These are east-facing vineyards, with ' similar to the . The various ' account for the differences in grape characteristics and explain the appropriateness of blending juice from different grape varieties and geographical areas within Champagne, to get the desired style for each Champagne house. Most of the Champagne produced today is "Non-vintage", meaning that it is a blended product of grapes from multiple vintages. Most of the base will be from a single year vintage with producers blending anywhere from 10–15% (even as high as 40%) of wine from older vintages. If the conditions of a particular vintage are favourable, some producers will make a vintage wine that must be composed of 100% of the grapes from that vintage year. Under Champagne wine regulations, houses that make both vintage and non-vintage wines are allowed to use no more than 80% of the total vintage's harvest for the production of vintage Champagne. This allows at least 20% of the harvest from each vintage to be reserved for use in non-vintage Champagne. This ensures a consistent style that consumers can expect from non-vintage Champagne that does not alter too radically depending on the quality of the vintage.