. A text-book of botany for secondary schools. Botany. HORSETAILS AXD CLUB-MOSSES 205 posed. In this exposed part archegonia appear, and therefore the large spore produces a female gametophyte (Fig. 197). In Selaginella, there- fore, the two kinds of sex-organs are produced by different plants, and we speak of male and female gametophytes. The connection of these two kinds of gameto- phytes with the two kinds of spores must be kept clear. The small spore (microspore) pro- duces the male gameto- phyte, and the large spore (megaspore) pro- duces the female ga- metophyte. It must be remembered, a
. A text-book of botany for secondary schools. Botany. HORSETAILS AXD CLUB-MOSSES 205 posed. In this exposed part archegonia appear, and therefore the large spore produces a female gametophyte (Fig. 197). In Selaginella, there- fore, the two kinds of sex-organs are produced by different plants, and we speak of male and female gametophytes. The connection of these two kinds of gameto- phytes with the two kinds of spores must be kept clear. The small spore (microspore) pro- duces the male gameto- phyte, and the large spore (megaspore) pro- duces the female ga- metophyte. It must be remembered, also, that with this change the gametophytes have become much smaller than they were before, and are no longer indepen- dent, in the sense of doing chlorophyll work. It follows that in the life-history of Selaginella there is an alternation of the sporophyte with two gametophytes. How this contrasts with the life-history of an ordinary fern may be indicated as follows: Fern: G::zS>o—S—o—Gzi°>o—S—o—Gn°>o—S, Fig. 197.—Female gametophyte of Selaginella, having burst through the wall of the mega- spore (m), and bearing archegonia (a) and rhizoids (r) upon its exposed part; somewhat diagrammatic. Selaginella: §~°>o—S: —o—G—o :S>o-S: :°>o, etc. 119. Coal.—The ferns, equisetums, and lycopods were associated together during the Coal-measures, and were the most conspicuous plants in the formation of coal. The formation of peat, already referred to (§ 101), indicates the. 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 Coulter, John Merle, 1851-1928. New York, D. Appleton
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