Transverse section through plum branch, from The Anatomy of Plants, Biodiversity Heritage Library
When I think of Nehemiah Grew (1641-1712), an image of a cross section through a stem appears in my mind’s eye (see above). I remember Grew as the creator of magnified images of plant tissue that have a rather inorganic feel to them in their rigid rows of cells. He was doing microscopic studies at about the same time as Robert Hooke, whose illustrations of plant cells are less regular, and somehow have a more organic feel. They were both attempting to communicate the new world they were exploring and trying to make sense of it. In an article to commemorate the tercentenary of Grew’s birth, the plant morphologist Agnes Arber (1941) noted that Grew held a mechanistic view of the universe and saw the microscope as a way to clear up mysteries of life by observing its constituents. Because of this viewpoint he also developed mathematical descriptions and was concerned with how to communicate the scale of objects seen under the microscope. This is a reminder that at the time there were no adequate standards of measurement for the microscopic world. So Grew used comparison to give his reader some idea of the size of what he was seeing, for example, that something was one-fifth the size of the cheese mite or the width of a marsh mallow seed.
Another major contributor to the beginnings of plant anatomy was the Italian Marcello Malpighi who like Grew was a physician, though Grew practiced medicine while Malpighi taught in a medical school and also did a great deal of research on animal anatomy. In fact, he began studying plants because he found animal tissue so complex and wanted to see if the “simpler” structures of plants could give him clues. Grew and Malpighi are usually mentioned together because in some ways, their work is similar. They labored independently without any knowledge of the other’s research until Grew produced a paper for the Royal Society of London (RS) shortly before Malpighi sent a manuscript read at an RS meeting. After that they followed and cited each other work.
The consensus is that they achieved similar results. Alan Morton (1981) claims that Malpighi saw more clearly than Grew in some details, but Grew’s culminating The Anatomy of Plants is the fuller and clearer work, with a more integrated view of plant structure. Agnes Arber (1942) also wrote a comparison of their contributions and contends that Grew may be better known because he wrote in English, while Malpighi published in Latin. Arber notes: “His Latin, though lively, is not very correct, and its interpretation is often by no means easy” (p. 15). But she considers Malpighi’s illustrations, made from his drawings, as excellent. Some of Grew’s illustrations are noteworthy because, while Malpighi made attempts at depicting microscopic structures in three dimensions, Grew did it more successfully.
Since this set of posts is on British botanists, I’ll end by noting some of Grew’s most important findings, though in many cases, Malpighi also produced similar results. Grew described the main anatomical differences between roots and stem. This required a great deal of work examining a variety of different species. The same was true of deciphering the vascular network in these structures. Grew admits that he got the idea for the spiral form of vessels from Malpighi, but he came up with the name “parenchyma” for the material packed around the vessels. While he depicted a great deal of order in plant tissue as orderly, he did not really conceive of cells as the basic unit of plant structure, though Robert Hooke had already coined the term for the structures he saw in cork cambium. Grew was able to differentiate between the scattered vascular bundles in monocots and the more ordered structures in dicots; he identified the medullary rays in dicot stems as well. Grew compared the cell walls to woven fibers and more generally compared a plant’s inner structure to a textile fabric. Arber (1913) quotes a long passage where he describes plant tissue as fine lace with an intricate and delicate texture. At one point he writes: “One who walks with the meanest Stick, holds a Piece of Nature’s Handicraft, which far surpasses the most elaborate Needle-Work in the World” (p. 54).
Grew also went into detail on the structure of flowers. Though he accepted the idea of sexual reproduction in plants, he wasn’t able to work out the process. He presented much information on seed structure in a variety of species and carefully observed seed development, coining the term radicle for the embryonic root. He also did simple experiments on the movement of sap, but his major work was anatomical. For a century and a half after Grew and Malpighi there was little further development in the field. It may be that it had to wait for the creation of better microscopes, or for further work in plant physiology. Or perhaps some of the lack of interest in the field may have been due to those images that so intrigue me. They presented such a well-developed, finished view of plant structure, that others might have considered the job of working out plant architecture to be complete. After all, plants were simpler than animals, how much more was there to know?
References
Arber, A. (1913). Nehemiah Grew (1641-1712). In F. W. Oliver (Ed.), Makers of British Botany (pp. 42–64). Cambridge, UK: Cambridge University Press.
Arber, A. (1941). Tercentenary of Nehemiah Grew (1641-1712). Nature, 147(3734), 630–632.
Arber, A. (1942). Nehemiah Grew (1641-1712) and Marcello Malpighi (1628-1694): An essay in comparison. Isis, 34, 7–16.
Morton, A. G. (1981). History of Botanical Science. New York, NY: Academic Press.
Herbarium World 