Had forwarded this to Dr. Rajendra Shinde, Department of Botany, St Xaviers College, University of Mumbai. He had in turn sent the images to Dr. S. Kaliamoorthy, Scientist, Botanical Survey of India. The information below is extracted from Dr. Kaliamoorthy's response.
Quite interesting photos. I presume it might be a leaf vein gall
caused by maggots. You must dissect the affected leaves and see for any
larvae. The following information I found in support of this, which
was, however, reported in Oak.
Vein Pocket Gall and Leaf Pocket Gall
galls are caused by the larval (maggot) stages of very small flies
called midges. Vein pocket galls are elongate swellings that occur
along mid- and lateral leaf veins of scrub and pin oaks. The process
begins when the unfolding leaves begin to flatten out. At this time,
the small midge lays its eggs. The tiny maggots move to the veins and
begin to feed. In a few days they are covered by gall tissue and
complete development by mid-spring. The mature larvae drop to the
ground and remain there over the winter. A related midge species causes
the marginal folds or leaf pockets that can be found on red oak or pin
oak. Several small larvae may be found inside the swollen folds of the
You can visit the above website for more info.