Special attention is drawn by Professor Engler to the fact (p. 130) that several of the Siberian plants inhabit the Alps and the Caucasus, but are not found in Scandinavia. And from this he deduces the conclusion that part of the Siberian flora migrated in a south-westerly direction towards the Caucasus and the mountains of the Mediterranean area, exactly in the manner indicated in respect to the fauna of the Alps. We learned that the migration to the Alps from Central and perhaps also parts of Northern Asia took a south-westerly course first, and was then followed by one in an easterly direction. I called the former the Oriental migration and the latter the Siberian. Later on Professor Engler states (p. 142) that the main mass of the Siberian forms of plants certainly wandered westward to the south of the Ural. This is proved by the numerous glacial plants found in the Caucasus, while the glacial flora of the Ural Mountains is poor. Finally, he expresses the opinion that the probability of most of the Alpine plants occurring in Arctic Siberia, having wandered from the Alps, by way of Scandinavia, Greenland, and North America, to North-eastern Siberia, is greater than the direct migration from Europe to Siberia (p. 143). Another continental writer on the Alpine flora who deserves special mention is Dr. Christ. His observation that Alpine plants by no means suffer from a high temperature (p. 309), but solely from a drying up of the soil, seems to me to point to the correctness of the view I have expressed on several occasions, that these plants have originated long before the Glacial period at a time when the climate was warmer and moister than it is now. It seems quite natural to Dr. Christ that the Arcto-Alpine flora should have originated in Asia, but he excepts thirty species which are absent from Northern Asia, though occurring in America (p. 327). These he thinks have penetrated direct from America to the Alps by way of Scandinavia, since no less than twenty-three still occur in the latter country. In the human population of the Alps, he continues (p. 336), one can distinguish an indigenous Celtic race, a Germanic colder and more apathetic race, and a more lively Roman one. The flora is composed of quite a similar mixture. We find also an indigenous element--an Arctic and a Mediterranean one. The last element is a survival of the Tertiary flora of the Central European plateau (p. 532). The plants were driven down to the shores of the Mediterranean, and it is only after the retreat of the glaciers that a few of them have been able to regain their ancient territory. The incoming Asiatic and North American flora likewise retired at the end of the Glacial period to the Alps and the Arctic countries, and left isolated traces of its former abundance on the North European plain. The bulk of the Arctic or Alpine flora is held to be of Asiatic origin. Since Siberia shows little trace