Professor: Please tell me about your project.

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

Professor: Where did Helmont conduct his experiment and when was it published?

Student: In Belgium in 1648.

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 was born between 1577 and 1580 and died in 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 (Website 1, Website 2, Website 3, Website 4, Website 5, Website 6) and encyclopedias in the library. When I did a google.com search for Helmont willow I got over 500 hits. 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 Helmont's description of his experiment off the internet. Helmont wrote "But I moystened the Earthen Vessel with Rain-water or distilled water (alwayes when there was need)..." 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 National Science Teachers Association internet site on Helmont's experiment said Helmont's "conclusion did not follow from the experiment.". It does not make sense to conclude the willow gained all its weight from the water when Helmont did not weigh the water added to the pot, and he found 2 ounces of soil missing. At least 2 ounces of the plant weight could have come from soil. 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 a "Helmont website" 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 floating 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. Bacon concluded "It seemeth by these instances of water,that for nourishment the water is almost all in all, and the earth doth but keep the plant upright, and save it from overheat and over-cold." Bacon showed plants could grow without soil before Helmont. 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?

Later

Parent: So what did the judge think of your project?

Student: I got an A but the judge didn't seem to know much about Helmont and his experiment. I thought college professors were supposed to be smart!

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 different version of Allchin (2000a) in an online-only journal).