Field Book: Pennsylvanian Plant Fossils of Illinois — Story, Setting & Ideas

The Time Chart as Structural Backbone

The time chart is the book's most deliberate structural device. It lists 19 entries, each with a number, a scientific name, and a brief note. For example, entry 13, Baiera, is described as a fossil leaf genus of ginkgo, whose only living representative, Ginkgo biloba, was “saved from extinction by careful cultivation in China.” The chart does not simply catalog; it tells mini-narratives of survival and loss. The inclusion of modern genera like Equisetum and Pinus alongside extinct ones like Sigillaria and Williamsonia creates a visual timeline of continuity and change. This chart is referenced implicitly throughout the book, as the same plant names reappear in the locality descriptions. The reader is expected to flip back to the chart to connect a fossil found in a specific county to its broader evolutionary context.

Recurring Images: Concretions, Shales, and Spoil Heaps

Three physical features recur with notable frequency: ironstone concretions, shales overlying coal beds, and spoil heaps from mines. The Mazon Creek area is introduced early as a classic locality where “ironstone concretions” yield well-preserved fossils. This image is echoed later in descriptions of Vermilion County, where fossils occur “in concretions much like those from Mazon Creek.” The phrase “shale overlying the … Coal” appears repeatedly, as in the Colchester (No. 2) Coal and the Herrin (No. 6) Coal. Spoil heaps are mentioned as accessible collecting sites in Saline County and elsewhere. These recurring details give the book a tactile quality: the reader is constantly reminded of the physical matrix in which fossils are embedded. The repetition also reinforces the idea that certain geological conditions are reliable indicators of fossil presence.

Movement from the General to the Specific

The book’s structure moves from broad overview to fine-grained local detail. After the time chart and a brief foreword, the text launches into a county-by-county survey of Illinois. Each county entry follows a similar pattern: name the county, mention a specific outcrop or mine, describe the fossil-bearing rock (often shale or concretion), and note which plant species have been found. For instance, the entry for Lawrence County mentions “coal balls” that preserve cellular structures. The entry for Saline County lists multiple coals—Murphysboro, Delwood, Willis, Reynoldsburg, Battery Rock—and directs the reader to “mine dumps” and “outcrops.” This repetitive structure is not monotonous; it trains the reader to expect certain kinds of information and to compare localities. The book ends with a section titled “Suggestions for Collecting,” which returns to general advice, creating a circular movement from overview to specifics and back to general principles.

The Role of Illustrations and Plates

Although the excerpts do not include the plates themselves, the text repeatedly references them, indicating that illustrations are integral to the book’s structure. Plate 4, for example, is described as containing Sphenopteris, Linopteris, Neuropteris, and other genera, each with a magnification factor (e.g., ⅗×). Plate 5 similarly lists reproductive structures like Codonotheca and seeds like Samaropsis. The captions serve as a visual index that parallels the time chart. The reader is expected to consult these plates while reading the locality descriptions. The illustrations by Marie E. Litterer are not merely decorative; they are a key part of the identification process. The book’s structure thus integrates text and image, with the plates providing a visual counterpart to the verbal descriptions of fossil forms and their occurrences.

The book’s value lies in its systematic approach: it provides a clear framework for understanding where and how Pennsylvanian plant fossils occur in Illinois, without overpromising on identification. Readers should use the time chart and plates as constant references while exploring the county entries. The recurring images of concretions and shales will help them recognize promising sites. This is a practical field companion, not a comprehensive treatise, and its structure rewards active, on-site use.

That gray afternoon, I kept returning to the coal ball photographs in Field Book, the way their roundness suggested something whole yet broken open. Hours vanished into Mazon Creek’s leaf shapes. Later, restless, I picked up another volume, and its quiet passages about cultivated soil felt like the same patient turning-over of earth. The Home Acre — Inside the Classic held that identical stillness, a gentle settling into patience.