244 THE JOURNAL OF INDIAN BOTANY.
woody climbers and of epiphytic mosses, lichens and ferns, and seed plants such as the Orchidaceae and Peperomia refleta of the Piper- aceae. The presence of epiphytes would indicate a dry season of less severity than is found in the coastal xerophyllous regions.
Pinus longifolia Formation.
Pinus longifolia occurs in almost pure forests in an altitudinal zone slightly lower than that of Quercus incana. On the steep north slope of the canyon separating Sat Tal from Naini Tal there are a few pines at 2,000 feet. Very little pine forest is seen, however, until 4,000 feet is reached, where it continues upward to about 6,500 feet. Hence it will be seen that it overlaps a small margin of the Bauhinia formation and over half of the oak formation. It however occupies an edaphic situation distinct from that of the oak. It occurs on the hilltops and ridges and more exposed flanks of the hills. On the north slope of the Sat Tal valley it descends from the crest to meet the oaks. On other hill slopes it descends from the crests along the ridges into the Bauhinia forest in much the same manner as the oaks ascend from the valley base along the stream channels. On peaks between 4,000 and 6,500 feet in height it is usual to find pines occupy- ing the highest and most exposed position. Higher peaks, such as are found a few miles further to the northeast, have pines only on the ridges, the summits being occupied by oaks.
Pinus longifolia is a strikingly xerophytic species. In May old leaves have mostly fallen while the new are appearing, so that the tree is almost bare. Much sun reaches the ground between the trees, and pine seedlings flourish, so the forest renews itself freely. The ground is covered most of the time by a layer of fallen pine leaves, which seem to prevent the extensive development of herbs and grasses. Shrubs are limited to such xerophytic pioneers as Aechman- thera. Other ^pecies of trees found sparingly mixed with the pines in the more sheltered parts of the forest are Englehardtia spicata, Castanopsis tribuloides and Myrica Nagi.
Factors Determining Distribution of Formations.
Clearly the monsoon forest is adapted to extremes of seasonal humi- dity and to a temperature which does not descend below freezing. The pine forest is adapted to dry exposures within certain altitudinal, hence temperature, limits. The Quercus incana forest is adapted to humid situations within altitudes slightly higher, hence temperature limits slightly lower, than those which make the upper and lower boundaries of the pine forest.
