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. 



Broad-leaved Sclerophyllous (Quercus incana) 

 Furmation. 



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 



