Dear 'Whichever,' what became of your avocado?

Now we know how to grow an avocado from a seed. We and ''Whichever.'' ''Whichever'' is the name of the correspondent who wrote of her avocado perplexities to the Boston Globe's ''Confidential Chat'' column, one of those open-letter forums that still continue an ancient custom of American newspapers.

Three pen pals (''Potted Fern,'' ''Bean Grower,'' and ''I've Got Daddy's Eyes'') provided definitive answers to ''Whichever,'' including the number of toothpicks (three or four) that one should stick into the seed to suspend it in a glass of water. ''Daddy's Eyes'' even quoted the California Avocado Advisory Board.

Rather remarkably, all three advisers agreed on their instructions to ''Whichever.'' Where else can a newspaper reader find a consensus these days?

Where else can a newspaper reader find what used to be known as Main Street?

Letter-chat forums are generally found in the style or life-style sections. The articles that surround them are smart and trendy, alert to the latest wisdom from pop psychology, full of ''In'' and ''Out'' lists, and partial to interviews with role-model superwomen like Jane Fonda, Gloria Steinem, and Shirley MacLaine.

In the midst of this '80s chic the letter-chat column can look as frumpy and old-fashioned as a woman in curlers shaking a dry mop out the window. The letter-chat writers seem stuck in the time-warp of - remember? - the old ''Women's Page.'' It is easy to be condescending toward these confidantes asking one another what to do with Brussels sprouts.

In a given week correspondents may be found tracking down a poem called ''Marjorie's Home,'' supplying tips for a new dog owner, and discussing the problem of babies who do not go quietly into the night.

This spring the Globe's ''Confidential Chat'' column celebrated its 100th anniversary with reprints. The basic subject matter - marriage, children, recipes - has changed surprisingly little over the years. Even the rhetoric has remained constant. A sentiment like ''Painful pages have been turned - but learned from'' could have been voiced in 1909. It happens to have been written in 1984.

We are, for better and for worse, in the presence of the unchanging rounds of daily life.

Sad little novels get hinted at more often than spelled out:

''My husband seems to be going through midlife crisis.''

''There are disappointments with some of the children.''

Details may be scant, but where else in a newspaper - or anywhere else - do ordinary feelings about ordinary life get expressed? Day after day the cry from the heart is heard: ''Someone out there must be suffering through a similar situation . . . and can give some hope to me at this time.''

The letter-chat column may be the last public place where one can hear voices interested in improving their lives rather than dramatizing them. The ''Chatters'' write out of undisguised loneliness, stuffing their little SOS messages into floating bottles addressed ''To Whom It May Concern.'' But in the act of writing, a measure of loneliness gets eased, and this week's seeker of help has a way of turning into next week's offerer of help.

In an oversophisticated world, tripping over its tricky paradoxes and flashy rationalizations, can we afford to despise these simple, unaffected, and heartfelt efforts to join the human race?

''Mocha's Gold'' makes the case for ''chatting,'' in all innocence, and with dignity:

''I write to thank you for the years of warmth . . . such a stage for sharing , debating, advising, laughing. Haven't we all reached outside of ourselves for a moment here or there - to touch another life? There is so, so much - so, so many - beyond the 'me.' ''

May the avocado-lovers still be writing 100 years from now.