Page:The Journal of Indian Botany.djvu/708

242 THE JOUENAL OF INDIAN BOTANY. Sapium insigne, the Stercufunalias, and Nyctanthes arbortristis the leaf buds do not open until the fruit is mature. Evidence for this is found in the fact that young non-fruiting trees often develop their leaves before the fruiting ones do so, that pollarded non-fruiting branches on fruiting trees are the first to leaf out, that the male trees of such dioecious species as Odina begin to leaf while the female trees bearing immature fruit show no signs of leafing, that trees which for any other reason are less cumbered with fruit are more prompt to leaf. Another example which might apply here is that Bauhinia retusa, which blooms in the autumn and matures its fruit early in the spring, is in full leaf before Bauhinia variegata, which blooms in the spring and matures its fruit later, has commenced to leaf.

An exposed hillside generally has a strikingly less leafy appearance in May than has a sheltered hillside or a ravine. Examination shows that this is because the floral population of the exposed hillside is made up mainly of such trees as Grewia, Nyctanthes, and Euphorbia, which are tardy in leafing, while the sheltered area has a larger number of evergreens and of early-leafing deciduous trees such as Bauhinia retusa. It is a matter of survival, for evergreens and Bau- hinia retusa could not persist in a place of severe exposure.

Almost all the vegetation is to a high degree deciduous. The leaf fall occurs irregularly, as compared with that of the temperate zone winter deciduous forest. Some of the trees are bare in October and others retain their leaves until just before the rains.

This forest is made up largely of evergreen trees and shrubs, but with an admixture of winter deciduous forms. Roughly about 60% of the species belong to the former and 40% to the latter class. The dominating tree is Quercus incana which is easily distinguished from the other Himalayan oaks by the silvery white lower surface of the leaves. It is the lowest of three altitudinal oak zones, and extends from the upper limit of the Bauhinia forest to about 8,000 feet. Quercus dilatata extends from 7,500 to 9,000 and Quercus semecar- pifolia from 9,000 to 11,000. The latter forms occur at altitudes higher than that of the Sat Tal valley. Q. incana renews its leaves in March and April, the other species somewhat later. At no time are the trees entirely bare, as the new leaves appear while the old ones fall.

Associated with the oak are three members of the Laurel family which occupy stream depressions and are probably hydrarch pioneers. Bhododendron arboreum and Pieris ovalifolia of the Heath family