. The principles of botany, as exemplified in the Cryptogamia. For the use of schools and colleges. Cryptogams; Plant anatomy; 1853. 82 COMPOUND ORGANS OF PLANTS. represents the Alsophila armata, a tree-fern of Brazil.* As the lower fronds decay and drop off, the young upper fronds gra- dually unroll and become pendent, and in this manner con- tinual additions are made to the height of the stem, and the growing point is carried upwards, the stem increasing in alti- tude, but not in diameter. 113. It is for this reason that these plants are called Acro- gens (axpo; a summit, and yiwdnv to produ
. The principles of botany, as exemplified in the Cryptogamia. For the use of schools and colleges. Cryptogams; Plant anatomy; 1853. 82 COMPOUND ORGANS OF PLANTS. represents the Alsophila armata, a tree-fern of Brazil.* As the lower fronds decay and drop off, the young upper fronds gra- dually unroll and become pendent, and in this manner con- tinual additions are made to the height of the stem, and the growing point is carried upwards, the stem increasing in alti- tude, but not in diameter. 113. It is for this reason that these plants are called Acro- gens (axpo; a summit, and yiwdnv to produce) or summit- growers, because they increase by additions of cellular and vascular matter to their extremities, and have no provisions for any subsequent increase in diameter. 114. Ferns, in their infancy, resemble the adult liverworts, having a green, flat, pro-embryo like the thallus of the frondose liverworts. This pro-embryo or pro-thallus afterwards gives rise to the proper stem and frond of the fern. In Fig. 34, s is. the spore of a fern, the Pteris longifolia, sprouting and giving off a rootlike process r, and a flat cellular expansion p, called the pro-thallus or pro-embryo. It is on this expansion that the antheridia and pistillidia occur, and the former having fulfilled * Richard's "Precis de Botanique," pt. i., , 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 Coultas, Harland, d. 1877; Stifle, Cloyd B. sgn. Philadelphia, Lindsay and Blakiston
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