. Introduction to cryptogamic botany. Cryptogams. 216 INTRODUCTION TO CETPTOGAMIC BOTANY. in this converge ; thus affording a ready method of ascertain- ing the genus in default of ; Harv. Mel. p. ^rnr Fig. 55. a. Tip of young frond of Bictyota dichotoma. h. Cell showing spiral structure. c. Threads produced from marginal cells in young fronds. d. Sorus of spores. e. Terminal cell in act of division. f. Ditto with a view to make two new centres of growth. All magnified.* Zonaria affords the well-known Turkey feather or Peacock's tail layer of our southern coasts and o
. Introduction to cryptogamic botany. Cryptogams. 216 INTRODUCTION TO CETPTOGAMIC BOTANY. in this converge ; thus affording a ready method of ascertain- ing the genus in default of ; Harv. Mel. p. ^rnr Fig. 55. a. Tip of young frond of Bictyota dichotoma. h. Cell showing spiral structure. c. Threads produced from marginal cells in young fronds. d. Sorus of spores. e. Terminal cell in act of division. f. Ditto with a view to make two new centres of growth. All magnified.* Zonaria affords the well-known Turkey feather or Peacock's tail layer of our southern coasts and of North America. The species are generally remarkable for their wedgeshaped fronds?, * I do not find the division of the cells as regular as figured by Nageli, (Die neuern Algensysteme, tab. 5, fig. 10—21,) who makes each circle of cells increase in geometric progression, nor do they all grow in regular lines. Great difierenees, in this respect, will be found in difierent specimens, or in different parts of the same specimen. Nageli was, however, the first to show the mode of growth. When the frond becomes forked, the termuial cell divides longitudinally, and then each half cell grows according to its own law. As the base of the new ceU assumes a circular outline, the cells which rise from its concentric and radiate division assume also a circular disposition, being as it were meridians of latitude to the meridians of longitude. The frond of Bictyota is peculiarly liable to be infested with species of Cocconema, which under a low magnifier look like little plant-lice. The calcareous Algse are also liable to the same 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 Berkeley, M. J. (Miles Joseph), 1803-1889. London, New York, H. Bailliere; [etc. ,etc]
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