The doomed sycamores along the Charles River-sources of grief for the Metropolitan District Commission, of spring rioting for Harvard students, and of long morning hours for the Cambridge minutemen--may not be sycamores at all.

A weekend check of Harvard botanists and horticulturists revealed that the sycamores, which are to be moved for the Memorial Drive underpasses, may in fact be London plane trees.

Hugh M. Raup, director of the Harvard Forest in Petersham, Mass., said yesterday that the trees along the Charles are "certainly not the typical American sycamore, which is found in the Midwestern United States but which is uncommon in the East." He said they were probably specimens of the "London plane tree, which has been widely planted in the East as a boulevard tree."

How About Buttonwood?

Peter S. Green, horticultural taxonomist at the Arnold Arboretum, said that he suspected the trees to be hybrids of the native American sycamore (also known as the buttonwood) and the Mediterranean species of plane tree. If they are, he said, "London plane would be a better name for them."

Green added, however, that the problem was complicated by "international ambiguity" in nomenclature. The London plane is often called a sycamore in the United States, and what Londoners call a sycamore is known here as a maple, he explained.

Pretty Much Alike

Donald Wyman, horticulturist at the Arboretum, said that the scientific name of the trees was platinus acera foils, and claimed that they could justifiably be referred to as sycamores. London plane trees and sycamores are "pretty nearly identical, anyway," he observed.

Although laymen use "sycamore" and "London plane" to refer to the same plant, it is "a real botanical question just what these trees are," Lorin I. Nevling, Jr., associate curator of the Arboretum, declared. Many people in New England call trees like those on Memorial Drive plane trees, he said, simply because the trees' bark comes off in long sheets and leaves a smooth surface.

Nevling pointed out that the Mem Drive trees might well be the result of crossbreeding done long ago. Whatever they are, the "very mature" trees are "superior plants" he said.