~Affinities of Panjab Flora.~--It is hopeless to describe except in the broadest outline the flora of a tract covering an area of 250,000 square miles and ranging in altitude from a few hundred feet to a height 10,000 feet above the limit of flowering plants. The nature of the vegetation of any tract depends on rainfall and temperature, and only secondarily on soil. A desert is a tract with a dry substratum and dry air, great heat during some part of the year, and bright sunshine. The soil may be loam or sand, and as regards vegetation a sandy desert is the worst owing to the rapid drying up of the subsoil after rain. In the third of the maps appended to Schimper's _Plant Geography_ by far the greater part of the area dealt with in this book is shown as part of the vast desert extending from the Sahara to Manchuria. Seeing that the monsoon penetrates into the province and that it is traversed by large snow-fed rivers the Panjab, except in parts of the extreme western and south-western districts, is not a desert like the Sahara or Gobi, and Schimper recognised this by marking most of the area as semi-desert. Still the flora outside the Hills and the submontane tract is predominantly of the desert type, being xerophilous or drought-resisting. The adaptations which enable plants to survive in a tract deficient in moisture are of various kinds. The roots may be greatly developed to enable them to tap the subsoil moisture, the leaves may be reduced in size, converted into thorns, or entirely dispensed with, in order to check rapid evaporation, they may be covered with silky or felted hairs, a modification which produces the same result, or their internal tissue may be succulent or mucilaginous. In the plants of the Panjab plains there is no difficulty in recognising these features of a drought-resisting flora. Schimper's map shows in the north-east of the area a wedge thrust in between the plains' desert and the dry elevated alpine desert cut off from the influence of the monsoon by the lofty barrier of the Inner Himalaya. This consists of two parts, monsoon forest, corresponding roughly with the Himalayan area Cis Ravi above the 5000 feet contour, and dry woodland of a semi-tropical stamp, consisting, of the adjoining foot-hills and submontane tract. This wedge is in fact treated as part of the zone, which in the map (after Drude) prefixed to Willis' _Manual and Dictionary of the Flowering Plants and Ferns_, is called Indo-Malayan, and which embraces the Malayan Archipelago and part of North Australia, Burma, and practically the whole of India except the Panjab, Sindh, and Rajputana. In Drude's map the three countries last mentioned are included in a large zone called "the Mediterranean and Orient." This is a very broad classification, and in tracing the relationships of the Panjab flora it is better to treat the desert area of North Africa, which in Tripoli and Egypt extends to the coast, apart from the Mediterranean zone. It is a familiar fact