Susan C. Mulholland

A Morphological Classification of Grass Silica-Bodies

Classifications of grass silica-bodies are constructed for various purposes ranging from botany to archaeology. Specific organizational details vary with the experience of the phytolith analyst and the condition of the material to be classified. The first step in classification of disaggregated phytoliths, however, must be consistent identification of types based on characteristics that survive burial, ie, morphology. The defined types then need to be correlated with plant taxa at as low a level as possible.

Phytolith shape frequencies in North Dakota grasses: a comparison to general patterns

Abstract Correlation of phytoliths from sediments to grass taxa is a complex process, even at the subfamily level. Grass phytolith taxonomies are reviewed and compared to the phytolith content of native North Dakota grass species. Phytolith production in the species examined generally follows reported patterns; however, significant deviations do occur, particularly in inflorescence material. Rondels (a “Festucoid” or trapezoid type) occur abundantly in all subfamilies. Dumb-bells are not restricted to the Panicoideae, although different morphological types may correlate to specific taxa. Saddles are not restricted to the Chloridoideae. Extensive examination of modern references (both plants and natural sediments) is required for accurate interpretation of fossil phytoliths. Refinements to reported patterns of phytolith shape frequencies in grass taxa are proposed in order to increase accuracy of identification of phytoliths from archaeological and natural sediments.

Phytolith Systematics: An Introduction

Phytoliths, microscopic mineral deposits in plants, have the potential for encoding significant archaeological and paleoenvironmental information. Although common throughout the plant kingdom and preserved under varied environmental conditions, only recently have phytoliths been examined in the systematic manner that yields data useful for interpretation. The most crucial area remains systematics—the description of shape and distribution data within the plant kingdom. Calcium phytoliths have been observed from the beginnings of microscopy, yet crystal and amorphous shapes are still described only in the most general of terms. Opal phytoliths have received much recent attention, but many plant taxa are yet to be carefully examined. A wide variety of approaches has been taken towards phytolith classification, often based on specific applications of the data. This volume presents some of the current research on various topics within phytolith systematics.

PHYTOLITHS FROM SOME ISRAELI SEDGES

ABSTRACT Phytoliths from grasses are well documented and broadly applied in some archaeo-botanical studies, whereas sedge phytoliths have received less attention. Since sedge phytoliths appear to be morphologically distinct from those in grasses, they may be of taxonomic importance. Phytoliths from nine samples of modern Cyperus and Scirpus grown in Israel were investigated. Light and scanning electron micrographs of phytoliths are presented. Scanning electron micrographs are included to illustrate high-resolution characteristics not readily visible under the more commonly used light microscope. It is hoped that the information regarding these Israeli sedges will provide plant taxonomists and archaeologists with a descriptive guide to the apparently small range of phytoliths produced by Cyperaceae.

Characterization of Grass Phytoliths for Archaeological Analysis

The word phytolith means “plant rocks.” Phytoliths are mineral deposits that form in and between plant cells. Any mineral deposit may be considered a phytolith, although most recent research has focused on opaline silica. Silica seems to be widespread in at least some plant families and is resistant to dissolution in a pH less than 9. Silica phytoliths therefore have the potential to be useful microfossils that can be helpful in the documentation of prehistoric environment and economy. Identifiable shapes rather than amorphous deposits are a necessary characteristic for useful microfossils. Several plant families have long been known to be consistent accumulators of identifiable silica bodies: Gramineae (grass), Cyperaceae (sedge), and Equisetaceae (horsetail). Phytoliths from the Gramineae are especially well known; specialized silica-accumulating cells produce distinctively shaped phytoliths. However, other families have also been shown to produce significant amounts of identifiable phytoliths. Ulmaceae (elm), Fabaceae (bean), Cucurbitaceae (squash), and Compositae (sunflower) are a few examples of dicotyledonous families that commonly produce phytoliths. Some families, such as the Labiatae (mint), have yielded little or no identifiable phytoliths to date. However, further study may indicate phytolith production in particular species.

Paleo-Indian Occupations in Northeastern Minnesota: How Early?

Environmental factors influenced Paleo-Indian occupation in northern portions of North America. Glacial features posed physical restrictions while revegetation on the post-glacial landscape limited available resources. Areas of northern Minnesota were ice-free by 13,500 B.P. with lake formation and revegetation at 12,000 to 11,000 B.P. By 11,200 B.P. northeastern Minnesota was probably habitable. However, archaeological evidence for early Paleo-Indian occupation in the area is sparse. Fluted and Holcombe-like projectile points have only been reported from three localities; well-dated sites are lacking at present, in contrast to the evidence for Late Paleo-Indian occupation. However, rugged terrain and thick vegetation hamper survey and bias the record toward accessible locations—those on modern waterways. A survey strategy based on the immediate post-glacial landscape needs to be implemented to address the question of earliest occupation. In addition, the problem of charcoal dates that are widely divergent from associated cultural remains must be addressed.