Botany Hall is designed to work as a unit. A sketch by Otto Jennings, Curator of Botany from 1915 to 1945, shows each corner of the room anchored by a different type of biome: arctic, desert, “local,” and tropics. Thus, viewers are positioned in an integrated network representing a whole spectrum of environmental conditions.
The four corner groups in the Hall vividly illustrate the three extreme types and one intermediate so placed in the one fairly small room that they can be most conveniently studied and compared with each other. From this standpoint, no museum in our country has a better set-up…The hall already contains the nucleus of what might be thought of as a fundamental outline or summary of the relation of vegetation to the main factors of temperature and moisture and in the Bog Group an illustration of ecological succession.
Subsequent curators remained faithful to this original vision as they kept up the hall and added new dioramas, which portrayed biomes that had unique characteristics, and/or were relevant to Pittsburghers. In 1976, in a memo to Dr. Craig Black, director of the museum, defending her idea for the herb exhibit, Dorothy Pearth explains this original conception by Jennings, and is also compelled to write that “Botany Hall did not just grow. Much thought has been given to it through the years.”
In addition to this, each “group,” as they were more often called in the early twentieth century, represents an integrated environment, and is specifically designed to show not just plants but delicately balanced relationships between various living things. Each diorama is accurate not just in terms of the types of flora and fauna depicted, but also in the sense that it is based on an actual spot out in the world, and for the most part, on a specific moment in that spot. When suggesting adjustments to the hall around 1940, Jennings argued that that a painting of a “marmot” on a rock in the Mt. Rainier group would be appropriate because he “saw one in a similar situation in that area,” justifying his suggestion based on his witnessing of an actual situation in nature, rather than, for example, on what botanically defines that environment. This photograph shows Elizabeth Niedringhaus (creator of plant models), Clifford Morrow (exhibition designer) and Leroy Henry (Curator of Botany) on the expedition for the Hemlock-Northern Hardwood group, where the team made casts of actual trees and mushrooms that they observed on their journey.
At the same time, crucial aspects of the dioramas work in other ways, portraying the biome not as one might witness it in person, but rather in a way that shows multiple stages of, for example, a flower’s life. The press release about the opening of the herb garden diorama notes that the plant models specifically show buds opening and also new shoots. While the herb garden diorama shows a time in May or June, Pearth wrote: “In order to show more flowers, we have telescoped the blooming period for some plants.”
It was also very important that the diorama be beautiful, and that it impress the viewer with the aesthetic qualities of nature. This was accomplished through artistic choices having to do with scale, color, spatial arrangements, and many other factors. The time of year shown in each environment was chosen at least in part for aesthetic purposes, because that is when flowers bloom or leaves change color. Jennings and Pearth both indicate in their writings their efforts to portray these natural sites at their most impressive, not separating artistic from scientific concerns. The dioramas also rely on the tradition of landscape painting and theatrical stage design as much as they do on the science of botanical illustration.
As well as the fabricated plants and flowers, the groups feature preserved flowers, leaves, and taxidermy animals, which operate as both a real thing and an idealized representation. The artists considered both the visual effect for the viewer, as well as practical concerns, when they selected materials to use. The end result does not much center on the viewer’s ability to discriminate between “real” and “fake.” Indeed, it relies on their inability to do so, on their distraction from this distinction. The diorama artists also used specific visual strategies to very carefully blur the transition between the two-dimensional and the three-dimensional parts of the diorama, contributing to the illusion that the space of the diorama extends infinitely, as if through a window.
Also included in the hall are shelves of individual plant models. Labels with images and numbered keys were used to help viewers identify plants, although today these have been replaced with photographic flip books. In the past the hall also featured oversized flower models with parts that could be taken apart, and at various times curators proposed maps and diagrams to enhance the hall’s content. Each of these representational strategies has its use, from depicting a situation holistically, to associating images with text, to zooming out from the hall to the whole country, or zooming in to see the inside of a flower.
 “Botanical Hall: Criticisms and suggestions,” c. 1940, p. 1, Jennings, from Botany section files.
 Pearth to Black, Carnegie Museum Memorandum, “Exhibits in Botany Hall…” April 21, 1976, from Botany section files.
 Niedringhaus article in Carnegie Magazine in 1973. Also useful – Memo from Netting to Morrow, April 24th, 1972, “Hardwood Forest Field Trip”
 “New Herb Diorama to Open at Carnegie Institute,” Carnegie Institute News Release, October 21, 1976, from Botany section files.
 “A Kitchen Garden of Herbs” draft label copy from Botany section files.