Liriodendron tulipifera flower

The University of North Carolina
A Department of the North Carolina Botanical Garden


Collectors of the UNC Herbarium
Information compiled December 2011 by Carol Ann McCormick,
Assistant Curator of the University of North Carolina Herbarium.

Hannah Thompson Croasdale
(8 November 1905  -  27 July 1999)

The University of North Carolina Herbarium has a handful of vascular plant specimens collected by Hannah T. Croasdale.  All were collected in Florida, and came to NCU as part of a gift from HNH in 2002.  The Harvard Herbarium database of botanists lists other herbaria holding her material as NH, PH, and L.  In 2014 Kevan Schoonover, a Charles T. Mohr Herbarium Intern at the University of North Carolina Herbarium, catalogued the University of Alabama’s algae collection as part of the MacroAlgae Digitization Project.  Several specimens collected by Croasdale from the Woods Hole, Massachusetts (signed “H.T.C.”) were found in the UNA collection.



The following information was taken from:



Hannah Thompson Croasdale, distinguished botanist, teacher, and humanitarian led an extraordinary but simple life. Hannah was born November 8, 1905; the second child of John P. Croasdale and Mary G. Croasdale, Quakers from Berwyn, Pennsylvania. Hannah had trouble walking as a youngster. Consequently, her mother chose to home school Hannah until age eleven, when she began private school. From the very start of her education, Hannah not only excelled academically but made it apparent that she loved to learn as well. The Croasdale family provided Hannah with excellent role models for a young woman interested in experiencing life. Her grandmother was one of the first female doctors in America, and Hannah's parents encouraged her to explore all her interests, not just those that traditionally fell in the women's sphere. The Croasdale's allowed Hannah to wear pants, romp around outdoors, learn carpentry, do yard work, and in general supported their daughter's intellectual growth.



In 1924, Hannah enrolled in the School of Education at the University of Pennsylvania, the only school in the University that accepted women. Even within the School of Education, the University did not permit men and women to take classes together. Thus Hannah, and four other women, had a separate, women's only, laboratory for their classes. During her years at the University of Pennsylvania, Hannah discovered her passion--algae. For the rest of her career, she passionately studied algae from many regions of the world. In 1928 Hannah received her Bachelor of Science degree and enrolled in the University's masters program.

Completing her masters in 1931, Hannah again stayed on at the University of Pennsylvania to study for her doctorate. Since Hannah's arrival at the University, the school had become more accepting of women, giving her the opportunity to take part in a wider range of classes and academic experiences. Hannah received her Ph.D. for her thesis on the Freshwater algae of Woods Hole, Massachusetts, in 1935. For her work, Hannah was rewarded with the Sigma Xi award and accepted into Phi Beta Kappa.

While working in Woods Hole at the Marine Biological Laboratory during the summer of 1935, Hannah heard of a job opening at the Dartmouth Medical school. Mr. Wm. Ballard hired Hannah, beginning a friendship that would last for many years.

After arriving in Hanover, Hannah never really left. She spent many years building her career at Dartmouth, at a time when the institution did not treat women well. Despite having a Ph.D., Hannah's first job was as a research assistant in the department of Physiology, earning a mere two thousand dollars per year, which even then was not near what a male Ph.D. would be doing or earning. It would take Hannah many years before she was actually in the botany department and even longer before she began teaching. The first course she taught, lab techniques, might not have been Hannah's passion, but she knew the subject matter very well and the students loved her. As a teacher, Hannah was as demanding and thorough as she was innovative and exciting. She inspired hundreds of Dartmouth students to love botany and was a true hero to many of her pupils. She had the patience to pursue a career that seemed to be going nowhere, the talent to command the respect of her colleagues and students, and the true dedication of someone who loved their work, both her algae and her teaching.

Dartmouth, however, was not quite ready for a women scientist, even one such as Hannah. The school did not treat Hannah as an equal to her male counterparts. Not until Hannah was fifty-three years old, did the college allow her to teach a course other than lab techniques. From there, Hannah still had to wait another ten years, until 1968, before the College made her a full professor, thirty-three years after Dartmouth hired her. For Hannah's part, she did not hold a grudge against the college or feel any bitterness towards the treatment she received. Hannah was content doing what she loved, recognition was insignificant in comparison. She herself spoke of the "whiny women's libbers." When fellow women academics approached Hannah in the 1960's about "de-marginalizing" women at Dartmouth, she felt they wanted "too much too soon." Hannah was the first woman to make her way through the ranks at Dartmouth. Her climb may have been slow but she remained passionate.

Hannah retired as a professor Emeritus in 1971, returning to Dartmouth each summer for seven more years to teach. Retiring did not mean the end of her academic pursuits. Hannah continued researching for another twenty years, classifying and making slides of Desmids.

During her career in phycology, the study of freshwater and marine algae, Hannah made many contributions
to her field and received many honors. Hannah was an authority on algae and Desmids, specifically from arctic
regions. She did field work throughout New England, Alaska, the Amazon Basin, England, and Scandinavia.
Every summer she returned to Woods Hole, Massachusetts to teach a course on botany and to continue her
research. To supplement her studies and her income, Hannah was a scientific illustrator, and a skilled scientific
translator. Speaking Swedish, Danish, Norwegian, and having a working knowledge of scientific Latin, the
scientific community counted on Hannah. She wrote hundreds of Latin diagnoses and translated several
technical books, as well as classifying species in Latin for many American botanists. Additionally, Hannah
was a founding member of the Phycological Society of the Americas and became its 21st president. She
belonged to the American Microscopical Society, the American Association for the advancement of
Science, the American Institute of Biological Sciences, the New Hampshire Academy of Science, and
the Dartmouth Scientific Association. The Finnish Societas pro Fauna et Flora, in 1968, awarded her
membership for her contributions to science, and later she was given an honorary chair at the Woods
Hole Marine Biological Laboratory.

Hannah led a full life. Though she never married, Hannah's friend Elmire Langlois Conklin described her as, "Mother, sister, aunt and cousin to the world." Hannah often rented space to students and visitors to the Hanover area. Often, these younger people would become lifelong friends, with Hannah taking on a vital role in their life. She helped one young couple through the birth of their first child; in return, they helped her through a hip replacement surgery. It was not that Hannah indebted people to her. She genuinely cared and the people whose lives she touched and was rewarded with love and affection.

Never one to shirk her duty, during World War II Hannah volunteered for the Hanover Fire Department,
becoming the first woman volunteer ever. As the smallest and the lightest, she was often the first one up
the ladder to fight the fire. When she moved to Norwich, Vermont in 1963, she retired from the force.
The department later honored her with a life membership with voting rights. Ironically, though tragically,
her volunteer hours did not help her fight a fire that destroyed her own house in 1989. Aside from
volunteering at the fire department, Hannah kept busy outside of her research, tending an organic garden,
doing carpentry, writing poetry, using her mechanical skills to make her own equipment, and being a
friend to many. In later life, a friend gave Hannah a puppy, Maggie, that inspired her to write a children's
about his adventures. Whatever she wanted to do, if Hannah set her mind to it, she would do.
Nothing could stop her, neither gender nor age.

Towards the end of her life, Hannah began spending her winters in Santa Rosa Florida, and her summers in Norwich. In 1994, she moved to Florida full time. In 1999, at the age of 93, Hannah died at her home in Florida.


The legacy of Hannah Croasdale's life is far more than professional accomplishments. Hannah helped
create a whole new generation of biologists who see her as a true hero, a woman who accomplished her
goals and enjoyed herself doing so. Though Hannah never fussed about being the first female tenured
professor at Dartmouth, it is part of her legacy, and part of why her students viewed her as a hero. Today,
Hannah continues to help create new biologists through the Croasdale Fellow in Vertebrate Zoology at
Dartmouth College and the
Phycological Society of America's Hannah Croasdale Scholarships, which are

designed to encourage graduate students to broaden their phycological training by defraying the costs of

attending phycology courses at biological field stations.


Wynne, Michael J. (2006)  Phycological Trailblazer No. 25:  Hannah T. Croasdale. Phycological Newsletter 42(2):  4-7. 
This article also has a list of Croasdale’s publications.

Hannah Thompson Croasdale was a major figure in 20th century studies on algae.  She was also a significant figure in her contributions to the Phycological Society of America in its early stages and throughout her long career.  In fact, she was one of the eleven “founding members” of the Society and the only female.  But she was always self-effacing, going about her work quietly but with dedication and resolve. Hannah was born in Daylesford, Pennsylvania, in 1905, two Quaker parents who encouraged her to always strive for lofty goals.  She attended the University of Pennsylvania, receiving her B. S. degree in 1928. Starting in the summer of 1930, she began working at the Marine biological laboratory in Woods Hole as a “botany collector” an instructor, and she continued to perform these duties for the decade of the 1930s under the mentorship of Wm. R Taylor, she pursued advanced degrees in botany back at Penn, earning the M.S. degree in 1931 and the Ph.D. degree in 1935.  Her dissertation publication, entitled “The Freshwater Algae of Woods Hole, Massachusetts” (which she published on her own in 1935) was awarded the Sigma Xi Prize for a thesis.

In 1937 Hannah joined the Dartmouth medical school as a research assistant. Then she transferred to working as a technical assistant in the Department of Zoology at Dartmouth College, holding that position up to 1953. She pursued her interests in the algae on her own time, on weekends and summer time. In the summers of 1939-1941, she co-taught a course on algae with Gerald W. Prescott at the University of Wyoming field station at Flathead Lake in Montana.  That Association led to a productive collaboration on their mutual research interests, especially the desmids. Starting in 1943 and on through 1950, she was an instructor in the summer algae course at the venerable Marine Biological Laboratory at Woods Hole, MA.  Her research was funded by grants from the National Science Foundation (1952-1955). Over the summers, by boat and by bicycle, she conducted her intensive survey of the distribution of both the marine and freshwater algal flora of Cape Cod. She displayed boundless energy, and in her prime she was known to swim without fear across the channel known as “Quicks Hole,” between Nashawena and Pasque Islands, where the currents are extremely dangerous when the tidal flow changes. Hannah was very generous in sharing her collections with others, as she did with Gronblad, sending him/her collections made over a three-year. In Vermont, New Hampshire, and in the area of Woods Hole, MA…

It was not until 1953 that she was granted faculty status (the rank of Instructor) at Dartmouth. She spent that some are doing fieldwork in the United Kingdom and in Scandinavia. The following year Hannah received a grant from the Arctic Institute of North America that allowed her to spend the summer collecting algae and mosses in various parts of Alaska. She was promoted to Research Associate with the rank of Associate Professor in 1959. Her attention turned to the freshwater algal flora of Alaska in the near early 1960s, and this work was also supported by NSF grants. In 1961 she was promoted to Research Associate with the rank of Associate Professor, but it was not until 1963 that she was permitted to actually give lectures at Dartmouth…

Although Dartmouth might have been slow to recognize the gem in their midst, the Phycological Society of America recognized Hannah Croadale’s achievements, electing her their Vice-President in 1964. It was that same year that Dartmouth promoted her to Associate Professor of Biology, with tenure. …

In 1967 she was elected President of the Phycological Society of America, and the following year she was named Full Professor of Biology, the first tenured woman professor at Dartmouth College. That was three years prior to her retirement…

There are plenty of “Hannah stories” that deserve repeating. Nina Allen relates how in the late 1970s and early 1980s she was teaching a phycology class at Dartmouth and how Hannah, the retired, was always around to help out Nina would take the class down to the MBL at Woods Hole every early October, and Hannah, then in her late 70s and with two new hip replacements (which the surgeon did not get quite even), would come along. Hannah’s in-depth knowledge of the algae around Woods Hole was invaluable.  Hannah, in waders, would accompany the class out to Cedar Swamp, “home of the biggest desmids you could find” on the Cape.  On one typical occasion, Hannah led the class into the swamp, in a pouring rain, and soon the water was over the waders, but nothing deterred Hannah from charging full ahead, full of energy and information to dispense. Her lifelong love of the algae was easily conveyed to the students, and they loved her for it.

For many years of her retirement years Hannah would spend half the year in her home in Vermont, just across the border with New Hampshire and near the Dartmouth campus, and the winter months in Destin, in the Florida Panhandle. In 1994 she made a permanent move to her Florida home at Santa Rosa Beach, and it was there on July 27, 1999, that she passed away at the age of 93.




   Curriculum in Ecology                 North Carolina Botanical Garden               Biology Department
      Curriculum                               North Carolina                                 UNC

         In Ecology                              Botanical Garden                   Biology Department


University of North Carolina Herbarium
CB# 3280, Coker Hall
University of North Carolina
Chapel Hill, NC 27599-3280
phone: (919) 962-6931
fax: (919) 962-6930

Last Updated: 29 December 2014