. A handbook of cryptogamic botany. Cryptogams. PH^ i\\ of the Laminariaceae and of other large marine Algse belonging to other groups display remarkable elasticity or other properties to enable them to resist the traction of the waves. In the larger species the frond is buoyed up by air-bladders. Janczewski describes the occurrence in the class of three distinct modes of growth, viz.— (i) The thallus and all its ramifications terminate in a generative apical cell which divides in a direction parallel to its base, and thus gives birth to a series of segments. This occurs in the Sphace
. A handbook of cryptogamic botany. Cryptogams. PH^ i\\ of the Laminariaceae and of other large marine Algse belonging to other groups display remarkable elasticity or other properties to enable them to resist the traction of the waves. In the larger species the frond is buoyed up by air-bladders. Janczewski describes the occurrence in the class of three distinct modes of growth, viz.— (i) The thallus and all its ramifications terminate in a generative apical cell which divides in a direction parallel to its base, and thus gives birth to a series of segments. This occurs in the Sphacelariaceffi and in Dictyo- siphon, but is the least common mode. (2) By peripheral growth, the marginal cells of the thallus are the youngest, and are more or less united into a generative peripheral zone (Myrionema, Grev., Leathesia, Gray, Ralfsia, Berk.). (3) By in- tercalary growth. This is much the most common mode, and there are, again, three modifications of it, viz. — I. The thallus terminates, when young, in one or more hairs, the common growing point of the thallus and of the hairs being situ- ated at their point of junction (Ecto- carpus, Desmarestia, Lmx., Carpo- mitra, Ktz., Cutleria, Sporochnus, Ag.). 2. The thallus is differen- tiated into three ' organs'—frond, stipe, and rhizoids; the growing point from which the stipe and frond originate is common to these two organs, while the rhizoids increase by apical growth (Laminariace^). 3. The absolutely undivided thallus is regenerated from the growing point situated at the base of the frond (Scytosiphon, Chorda, Punctaria, Grev., Asperococcus, Lmx.).' Literature. Magnus—Festschr. Gesell. naturf. Freunde, Bprlin, 1873. Areschoug—Bot. Notis., 1873. Gobi-Bot. Zeit., 1877, p. 425. Reinke—Ibid., p. 441. Thuret & Bornet—Etudes Phycologiques, Fig. 214.—Lessonia fitscescens Bory (greatly reduced).. Please note that these images are extracted from scanned page images that may have been digitally
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