. The evolution of plant life, lower forms. Cryptogams; Plants. i6 PLANT LIFE. growing in the air is an absolute necessity. It is generally admitted that the entire land vegetation originated from sea-weeds, and by various phases of evolution attained to the great variety of form and structure existing at the present day; and during the early attempts of seaweeds, the pioneers of the vegetable kingdom, to gain a footing on dry land, they were confronted with the unforeseen difficulty of counteracting the grave danger resulting from dessication. Primitive attempts to overcome this difficulty ar
. The evolution of plant life, lower forms. Cryptogams; Plants. i6 PLANT LIFE. growing in the air is an absolute necessity. It is generally admitted that the entire land vegetation originated from sea-weeds, and by various phases of evolution attained to the great variety of form and structure existing at the present day; and during the early attempts of seaweeds, the pioneers of the vegetable kingdom, to gain a footing on dry land, they were confronted with the unforeseen difficulty of counteracting the grave danger resulting from dessication. Primitive attempts to overcome this difficulty are seen in such microscopic aquatic forms as Palmella, Glceocystis, and. Fig. 2.—Pandorina, trwrum (x 400). A, a motile colony (or coenobium). The individual cells have their cilia protrading through the gelatinous envelope of the colony. B, two zoogonidia, formed by the division of the cells oiA, in process of conjugation. (From Prantl.) Nosioc, where numerous individuals become agglutinated together by a secreted substance very retentive of water, thus forming colonies frequently of considerable size; other kinds form dense felt-like masses, as Spirogyra and Con- ferva. Such collections of individuals present no approach to anything like specialization of parts or division of labour,. 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 Massee, George, 1850-1917. London, Methuen & Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectplants, bookyear1891
