Ferns are a group of plants that illustrate many changes in taxonomic concepts which are useful in establishing systems of classification and in the delimiting of genera and species. The Linnaean genera were distinguished on such gross morphological features as the shape, size, and placement of the sori. Later, stelar anatomy became an important criterion. Then such items as venation, origin of the sorus, indusium, development of the sporangium, scales, hairs, glands on the indusium, chromosome number, and, to a lesser extent, spore morphology were used to separate species. This is not a definitive paper on the use of spore morphology in fern taxonomy but rather an assessment of the role that may be attained by this much neglected field. The concept of the structure and the terminology applied to different portions of the spore is quite varied. Douglas H. Campbell (1905) described spore structure as follows: "The young spores are thin-walled, but later the wall becomes thicker and shows a division into two parts, an inner layer, which generally shows a cellulose reaction and is called the endospore (intine), and an outer more cuticularized coat, the exospore (exine). In addition, a third outer coat (perenium, epispore) is very generally present." Structurally, the spore consists of a protoplast, the living portion encased in a thin layer, the intine, which is surrounded by the exine. This in turn is generally enclosed by one or more layers which have been termed perispore, epispore, perine, or sclerine by various authors. There is no unanimity of usage among those interested in spore morphology. It was recognized early that differences in the number and orientation of cleavage planes gave rise to two types of spores from the spore mother cell, namely, the tetrahedral and bilateral spores. These were so named because, in the case of the former, three planes or faces were common to the proximal side of the spores tetrahedral or bilateral, and Coniogramme with spores 6