Orchids activity

Research assistants with the Darwin Correspondence Project joined the teaching team for a new Freshman Seminar at Harvard College called “Getting to Know Darwin.” The class was composed of first year undergraduates and was taught by Ned Friedman, Director of the Arnold Arboretum at Harvard University and Professor in the Department of Organismic and Evolutionary Biology. Here is a link to a feature about the course.

 

Students observe an orchid of the genus Catasetum.

Although Darwin’s observations of orchids provided many useful examples of evolution by natural selection, Darwin saw this work as more of an enjoyable past-time than a rigorous academic endeavour. This attitude towards his work on orchids is shown in an 1860 letter Darwin wrote to the American botanist Asa Gray, in which he stated:

“Not being able lately to work I have amused myself about Orchids. I have been struck with amazement at beauty of contrivances with respect to fertilisation by insects.”  

 

After reading a selection of letters about Darwin’s work with orchids and Chapter 1 of Darwin’s 1862 book On the various contrivances by which British and foreign orchids are fertilised by insects, the students found it useful to learn about orchids in a more experiential environment. To this end, the students visited the collection of glass flowers in the Harvard Museum of Natural History. These glass flowers were made by German glass artisans Leopold and Rudolph Blaschka from 1887-1936. The flowers were originally created for Professor George Lincoln Goodale as a means of teaching botany. 

 

A student inserts her finger into an orchid to see if it will eject its pollinia onto her finger.

In addition to visiting this collection, the students were able to conduct the experiment Darwin describes on pages 14-16 of On the various contrivances by which British and foreign orchids are fertilised by insects. The experiment is simple – all you need is an orchid of the genera Catasetum. This genera of orchid uses a pollen release mechanism that ejects pollinia onto insects as they enter the orchid. To activate this pollen release mechanism, students need only push a finger or a pencil into the orchid. Just as Darwin describes, the pollinia will be ejected onto the students’ fingers or pencils, allowing them to appreciate, firsthand, this fascinating method of fertilization.

 

Lastly, the students watched a few video clips that illustrate the various ways in which orchids are fertilized. Interesting videos are available here and here.

 

Orchids teaching module main page