In the North of Europe, which has furnished us with our standard information regarding the Neolithic culture-stratum, the certain proofs that have hitherto been found of agriculture and the cultivation of useful plants having been practised at that time (to which civilisation owes no less than to the breeding of useful tame animals) consist not so much of plant remains themselves as of stone hand-mills and spinning and weaving implements, which indicate the cultivation of corn and flax. [Sidenote: History in the Lake Dwellings] Our chief knowledge of Neolithic agriculture and plant culture has been furnished by the lake-dwellings, especially those of Switzerland, which have preserved the picture of the Neolithic civilisation of Central Europe, sketched for us, as it were, in the North, in its finest lines. So far we can prove the cultivation of the following useful plants in the later Stone Age; their remains were chiefly found, as we have said, well preserved in the Stone Age lake-dwellings of Switzerland, which have been described in classical manner by Oswald Heer. Of cereal grasses Heer determined, in the rich Stone Age lake-dwellings of Wangen, on Lake Constance, and Robenhausen, in Lake Pfäffikon, three sorts of wheat and two varieties of barley--the six-rowed and two-rowed. Flax was also grown by Neolithic Man. This was, it seems, a rather different variety from our present flax, being narrow-leaved, and still occurs wild, or probably merely uncultivated, in Macedonia and Thracia. Flax has also been found growing wild in Northern India, on the Altai Mountains, and at the foot of the Caucasus. [Illustration: THE DEVELOPMENT OF THE HORSE The horse which was common in the Stone Age was a wild ancestor of our own domestic horse, but not quite so large or so strong as the average well-bred creature familiar in our modern life. Its remotest ancestor was the Hyracotherium, or Orohippus, while an intermediary stage was that of the Hypparion, or Protohippus, in which, as shown in the diagram, the change from the foot to the hoof had advanced to a very great extent.] The common wheat occurring in the lake-dwellings of the Stone Age is a small-grained but mealy variety; but the so-called Egyptian wheat with large grains also occurs. [Sidenote: Gardening in the Stone Age]