. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 348 MOSSES AND FERNS CHAP. the growth of the prothallium is exactly opposite to that of the first rhizoid (bi-polar germination), and Kny ((5)» P- ^^) lays a good deal of stress upon this, as distinguishing Osmunda from the Polypodiacese; but it is not at all uncommon for O. Claytoniana, especially, to have the axis of growth of the rhi- zoid almost or quite at right angles to that of the prothallium, exactly as in the Polypodiacese. Where the germination is truly bi-polar the exospore is push

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. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 348 MOSSES AND FERNS CHAP. the growth of the prothallium is exactly opposite to that of the first rhizoid (bi-polar germination), and Kny ((5)» P- ^^) lays a good deal of stress upon this, as distinguishing Osmunda from the Polypodiacese; but it is not at all uncommon for O. Claytoniana, especially, to have the axis of growth of the rhi- zoid almost or quite at right angles to that of the prothallium, exactly as in the Polypodiacese. Where the germination is truly bi-polar the exospore is pushed up with the growing pro- thallium, and appears like a cap at its apex, but if the rhizoid is lateral, the exospore remains at the base. In O. Claytoniana there are usually several transverse walls A-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Campbell, Douglas Houghton, 1859-1953. New York, The Macmillan Company;

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