Some 200 readers corrected my statement that supermarket clerks earn less than professionals do. They cited many instances in which people with professional training make less than grocery clerks.

Mary Keas now adds a profession we overlooked the first time around.

"I'll bet," she writes, "that it's been a long time since you looked at the "Help Wanted' adds in Editor & Publisher. I always check them, just for the heck of it. Would you believe $125 a week for a reporter? And not for just a recent J-school graduate, either. They want somebody with experience. Salaries commensurate with supermarket scales are available to Ph D types."

When I was an E&P subscriber, Mary, I always looked at the want ads, and then counted my blessings. I haven't looked recently because I no longer subscribe to the magazine. In those days, E&P steadfastly refused to refer to the American Newspaper Guild by its right name. Even in a first reference, it was always "the guild," not even capitalized.

I sent them a letter of protest and asked for an explanation. They ignored me, so I began ignoring them.

I agree with you that it is unsettling to find that in some quarters college-trained journalists are still rated at little more than a dime a dozen. What unsettles me even more is the realization that the advertisers must be getting plenty of applicants at those rates.

Oh, well. Look at the brighter side. If President Carter's wage-price guidelines go down the drain, journalists won't get the blame for it.

A TREE GROWS IN MARYLAND

On second thought, $125 a week may be more than some of us are worth. A notable example would be the reporter who wrote about an auto that struck a tree on the Maryland side of Westmoreland Circle a month ago.

It grieves me to inform you that he said the car seemed to be embedded in the tree and might therefore begin to rise from the ground as the tree grew.

It grieves me even more to inform you that I was the one who wrote that.

When Lansing L. Joralemon wrote to tell me that trees grow taller from the top, not the bottom, he asked whether anybody else had commented on my mistake.

Well, yes. Now that you mention it, Lansing, 32 people wrote to tell me that an object imbedded in a tree (a hammock support, for example) does not rise as the tree grows. Nor will heart-enclosed initials carved in a tree's trunk ascend skyward as the years pass. Mathew C. Rainey wrote: "As a tree grows, its added height comes only from new growth at the top. At the same time, a new layer (or tree ring) grows all around the tree each year."

Architect Clifford G. Himes wrote: "A nail placed 2 feet above the ground in the side of a tree would still be 2 feet above the ground 20 years later."

Flo Gordon of Springfield wrote: "Even little children know that a tree's upward growth is only at the top. Otherwise their swings would soon be out of reach."

A botanist at the Beltsville Agricultural Research Center (I'm sorry, but I can't decipher his signature) wrote: "Trees do not grow from their bases. There is no basal meristem. They grow from their apical meristems." Under "apical," my dictionary says, "relating to or situated at the apex." Under "meristem" it says, "a formative plant tissue, usually made up of small cells capable of dividing indefinitely and giving rise to similar cells."

The opinions expressed above were echoed in letters from William M. Hawkins Jr. of Potomac, Richard Battey of Annandale, Esther A. Andrews of Silver Spring, Dave Kirtley of Silver Spring, Harry Louis Selden, Henry W Petrie of Fairfax, Edward Driscoll of Poolesville, Jay W. Hutchings of Laurel, John P. Mann of Beltsville, Peter S.P. Hui of Silver Spring, Nancy Snyder, Joe Gerber of Bethesda, Mark S. Hruby, Paul L. Powell of Alexandria, Marie Harbourne of Fairfax, Bob Dante of Beltsville, Leonard J. Czajkowski, Leland W. Smith of Crofton, Ray Cassidy, John R. Blowers of Falls Church, John W. Willis and several people who didn't sign their names or didn't sign names I could read.

Willis was the only one who offered balm for my wounds. "Time magazine and the Wall Street Journal have made the same error," he wrote, "so our are in good company."

Thanks, but I would have preferred to join that distinguished company because of my acumen rather than my stupidity. I'm afraid I didn't earn my $125 last week.