Among the many calls, e-mails and letters that followed my story on mugwort, yomogi and the elusive lin sai cake was one from a reader who chided me for doing insufficient research.

Well, Mr. Mow, you were right. I made a mistake. The story begins with reader Robin Fong's request for a recipe for a seasonal Chinese rice cake, lin sai biang. Several readers responded with recipes, but all called for lin sai flour — which was nowhere to be found.

My mistake was in pursuing, and ultimately accepting, a suggestion that the herb used in lin sai biang is the same as one used in Japan for another type of rice cake. That herb is yomogi, or mugwort.

Because mugwort and the lin sai plant are used in similar ways, Internet research seemed to support the idea that the two were one and the same. So did a day of making mugwort cakes with volunteer tester Marylene Chun. Chun recalls making the cakes with her grandmother and the ones we crafted — flat, chewy-gelatinous hunter-green confections pressed into oiled wooden molds — tasted right to her. She was convinced we'd found the elusive lin sai herb. So was I.

Wrong.

The minute my story appeared with pictures of mugwort, readers began writing to say that, while Chinese do use mugwort for some purposes, lin sai is something else. But no one who called knew the English name of the plant.

Then Hazel Yee came forward, a woman who had worked at the University of Hawai'i at one time and had, years ago, asked experts at the Department of Agriculture what the herb might be. It was identified as Pluchea indica (L.) Less, known as Indian fleabane. Amy K.C. Ching of 'Alewa also wrote to say that, once when her brother was taking a gardening course at the University Extension Service station, he confirmed that lin sai is P. indica.

Marie C. Neal's classic "Gardens of Hawaii" (Bishop Museum Press, 1948) says the introduced plant grows near the coast in salt marshes, on coral plains and coral fills, as well as inland. "Handbook of Hawaiian Weeds" by E.L. Haselwood and G.G. Motter with Robert Hirano (University of Hawai'i Press, 1966) describes it as a weed with no forage value.

But Cantonese here considered lin sai a highly prized forage plant: They picked it along the banks of the Ala Wai, Nu'uanu stream and the salt marshes of Damon Tract (lower Kalihi, near Nimitz). It still grows in some of these areas, but people today hesitate to use the plant from the wild because of pesticide spraying or other contamination. Some people grow it in their yards.

In defense of Marylene's conviction that the cakes we made had the right flavor, Indian fleabane is a relative of mugwort. Both are in the family Asteraceae (formerly Compositae), the same family as chrysanthemums, daisies, asters, chamomile and zinnias. The taste of both mugwort and Indian fleabane remind me of chamomile.

I begged readers for a sample of the plant so it could be identified and photographed. One reader mailed a sprig to me, but it got moldy before I got back from vacation.

The Rev. Duane Pang, a Buddhist priest from Liliha who was on vacation in China when the original article ran, invited me to drop by the temple where he lives to pick a spray from his backyard bush.

Pang is certainly one of the last people in Hawai'i — possibly the very last — to make lin sai biang by the traditional method, which is so physically demanding that he has to recruit the youth of the temple, many of them martial artists, to help him.

Before he described the whole process to me, Pang gave me a short course in terminology. In sai — the name by which some readers mistakenly know the plant — means parsley. The correct name is lin sai (sometimes spelled lien sai) and the cakes are lin sai biang. He said the cakes are a regional specialty of Guangdong (Pinyin spelling, Canton) province.

Lin sai biang are served on the eighth day of the fourth lunar month, which usually falls in May. Pang has heard two reasons for this: In Taoist circles, this festival is considered to be a time when you can change your luck (presumably for the better), because it is the birthday of the General of the Changing Luck. Cakes are offered to this deity to assure better fortune.

In Buddhist tradition, it's Buddha's birthday, a time of cleansing and renewal. Lin sai is known throughout Asia as a medicinal herb, good for the liver and for "cleaning out the system." Cakes are given to family members to eat both as a celebratory treat and for good health.

Pang's grandmother called lin sai biang "worm cake," because she believed it would banish worms from the body. (My grandmother was also preoccupied with worms — but we didn't get cakes as a cure.)

About the second day of the eighth month, Pang collects a bundle of leaves from his mother's immense bush in Kaimuki and places them in the sun to dry for a few days.

He hauls out the hefty mortar given him by a friend whose mother-in-law got too old for making lin sai biang. It's a square of stone with a hollow bowl carved in it. He mixes 5 pounds of raw long-grain rice with the dried lin sai and he and his well-muscled assistants spend the better part of a sweaty day pounding and smashing this mixture into a flour, using a pestle made from a heavy piece of pipe. The flour is sifted through a bamboo strainer and then dried for a couple more days.

On the seventh day of the fourth month, he boils sugar and water together, then dumps in the dried lin sai flour, forming a very stiff mixture, which then must be kneaded to just the right degree of smoothness and pliancy.