Generally, spores (PI. 11-11, figs. 1-14) are the reproductive bodies of the 

 nonflowering plants, whereas pollen grains (PL 11-11, figs. 15-29) are the male 

 reproductive bodies of the flowering plants. Morphologically spores are char- 

 acterized by sutures, and pollen by furrows and pores. These sutures, furrows, 

 and pores are associated with the germination process and serve as openings 

 through which the plant reproductive cells escape. 



Plant spores, having been studied more extensively than pollen, are better 

 understood; therefore, their classification is better established. 



The oldest known spores of vascular plants are from the Silurian. Lang 

 and Cookson (1935) reported plants possessing cuticles, stomata, and lignified 

 vascular tissue from the Silurian rocks of Australia. Until the discovery of spores 

 in the Silurian of New York State, the oldest known spores in this country were 

 from the Devonian. Although spores have been reported from pre-Silurian 

 rocks, most of these reports come from areas where the structural and strati- 

 graphic sequences are poorly controlled. The writer knows of no undoubted 

 vascular plant remains from pre-Silurian rocks. 



The earliest pollen grains are found in Carboniferous rocks, although it is 

 not until the Cretaceous that angiosperm pollen are encountered in abundance 

 and variety. The Permian and Triassic pollen are from the gymnosperms (PL 

 11-11, figs. 15-19), which are similar to the modern pines, spruces, cycads, and 

 hemlocks. The earliest known angiosperm pollen (PL 11-11, figs. 20-29) occur 

 in the Jurassic. 



Trichomes (PI. 11-1, figs. 20-22) 



Trichomes, or epidermal hairs, which are usually hair-like branching or 

 plate-like outgrowths of the epidermis of plant leaves and stems, are found in 

 sediments from Silurian to Recent. They should be useful to the paleontologist 

 when better understood. Because they are cellulose, the trichomes are found in 

 the residues prepared for other acid-insoluble microfossils. 



Leaf Cuticles (PI. 11-1, figs. 16, 17) 



The outer films and epidermal cells with stomatal structures are the leaf 

 cuticles which currently are being used to a minor degree in microfossil work. 

 Like the trichomes, their geological range is Silurian to Recent. Histograms of 

 cuticles from the same coal over a wide areal extent show remarkable similarity 

 (Wilson and Hoffmeister, 1956). These forms are insufficiently understood to 

 be useful in narrow stratigraphic determinations, but appear to have some eco- 

 logical significance by indicating the type of vegetation that was localized within 

 a particular vicinity. 



213 



