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Return to: Two Views on Helmont's Willow Experiment

Modern Day Scenario:

(College biology professor judging a school science fair project on Helmont's experiment.)

Professor: Please tell me about your project.

Student: For my project I repeated Helmont's willow experiment but used a spider plant.

Professor: When did Helmont publish his experiment, and where did Helmont conduct his experiment?

Student: In 1648 in Belgium.

Professor: I don't think you have the historical context correct. Helmont was a "sixteenth-century Dutch physician" (Allchin 2000a, 2002b)

Student: What's historical context? Helmont was born in Brussels, Belgium so that makes him Belgian doesn't it? He lived from 1577 to 1644 so he lived mainly in the 17th century, didn't he? His willow experiment definitely was published in 1648 after his death. I got this information from several websites and encyclopedias in the library. It's in my report.

Professor: Oh, I'm sorry. You do seem to be right after all. Please tell me about your methods.

Student: I placed 200 grams of dry soil in a pot, then planted a spider plant that weighed 20 grams. I watered the plant with distilled water for 3 months. After 3 months, the plant weighed 120 grams, and the dry soil weighed 199 grams.

Professor: How could you use distilled water, you ruined the historical context! Didn't your teacher tell you that "Concerns about distilled water in the context of an experiment done centuries before anyone understood the concept are grossly misplaced." (Allchin 2000a, 2002b).

Student: Huh? What's historical context? This is a biology project. Helmont said he used distilled water or rain water.

Professor: [Paging through a copy of Allchin (2000a).] He did?

Student: Yes, I got a description of his experiment off the internet. It's in my report.

Professor: Oh! Never mind. Let's move on. What was your conclusion?

Student: I concluded that only 1 gram of the plant weight came from the soil. So plants do not gain much of their weight from the soil.

Professor: Oh no. You must conclude that plants arose from water alone to maintain the historical context! Remember, "van Helmont's experiment was well designed and interpreted appropriately in the context of its own time." (Allchin 2000a).

Student: But this is 2003, not 1648. The internet sites on Helmont's experiment said he made the wrong conclusion from his data. It's in my report.

Professor: [Nervously paging through the copy of Allchin (2000a)] Really? So where do you think your 100 gram gain in plant weight came from?

Student: From carbon dioxide in the air.

Professor: No, no, no. Remember, carbon dioxide was "a substance wholly outside his (Helmont's) conception" (Allchin 2000a).

Student: But Helmont coined the word gas and determined that when he burned 62 pounds of oak charcoal, he got 61 pounds of carbon dioxide and 1 pound of ash.

Professor: Huh? Where did you get that information?

Student: From the Helmont sites on the internet. It's in my report.

Professor: Anything else?

Student: Yes, I also grew a spider plant in water instead of soil to see if the plant could grow without soil. .

Professor: What? How can you be so insensitive to the historical context? Don't you know that "Helmont was also probably well aware that plants do not grow outside soil. There was certainly no existing evidence then to suggest that the substrate of soil was not relevant in some respect." (Allchin 2000a)

Student: But what about aquatic plants like duckweed in the aquarium in our classroom? Didn't duckweed exist in 1648?

Professor: Well, yes, it certainly did exist.

Student: I also read on the internet that Sir Francis Bacon reported that he grew terrestrial plants in water in his 1627 book. It's in my report.

Professor: [Tearing up the copy of Allchin (2000a)] You don't say. You gave an excellent explanation of your project. By the way, could I please get a copy of your report?

Literature Cited

Allchin, D. 2000a. How not to teach historical cases in science. Journal of College Science Teaching. 30:33-37.

Allchin, D. 2002b. How not to teach history in science. The Pantaneto Forum. July. (This is a slightly edited version of Allchin 2000a in an online-only journal).