. Elements of botany. Plants. SOME TYPES OF FLOWERLESS PLANTS. 225 latter, are not certain hereafter to be recognized in any strictly scientific classification of cryptogamous plants. Algae vary in size from spheres yorViTTy ^^^^^ ^° diameter to great cable-like masses many hundreds of feet in length. Some species are found in salt, some in brackish, some in fresh water. There are species which occur growing on snow and melting ice, while others form the characteristic vegeta- tion of hot springs, in which they sometimes endure a tem- perature nearly equal to that of boiling water. 275. Reprod
. Elements of botany. Plants. SOME TYPES OF FLOWERLESS PLANTS. 225 latter, are not certain hereafter to be recognized in any strictly scientific classification of cryptogamous plants. Algae vary in size from spheres yorViTTy ^^^^^ ^° diameter to great cable-like masses many hundreds of feet in length. Some species are found in salt, some in brackish, some in fresh water. There are species which occur growing on snow and melting ice, while others form the characteristic vegeta- tion of hot springs, in which they sometimes endure a tem- perature nearly equal to that of boiling water. 275. Reproduction hi Algcv. — The reproductive processes in algae are of several types, which are described in special treatises but cannot be ex- plained in detail in a botany for beginners. Besides the mode by formation of zoosjwr^es, as in the Protococcus, and that by the formation of zygospores^ as in the desmids and in Spi- rogyra, there is a very interest- ing method which maybe briefly outlined here, because it repre- sents an important principle in many kinds of reproduction, the unio7i of fertilizing cells with much larger egg-cells. This kind of union is well illus- trated by one of the very com- monest of seaweeds, the common bladder-wrack or rockweed. Fig. 196, which grows on rocks between high and low water mark. It has many flat, leathery branches, which are buoyed up in the water by the air-bladders, h. The spores are pro- duced by means of a rather complicated set of organs con-. FiG. 196. — Common Bladder-Wrack or liockweed, Fuciis vesiculosus. <Re- duced to about % the natural size.) h, air-bladders ; /, organs for produc- tion of 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 Bergen, Joseph Y. (Joseph Young), 1851-1917; Bergen, Joseph Y. (Joseph Young), 1851-1917. Bergen's Botany: k
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectplants, bookyear1896
