The most important positive evidence on this point indicates that the most ancient Gymnosperms were derived from the Filicales rather than from any other phylum of the Vascular Cryptogams. Extinct forms are known intermediate between the Ferns and the Cycads, and a number of these have been shown to bear seeds and must be classed as Pteridospermae. [Please select]
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The discolouration and decay are not caused by parasitic cryptogams, which were observed by Fritz Müller in only a single instance. [Please select]
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The directions are made fullest in relation to cryptogams and physiology, because these fields are at present most unfamiliar to teachers. [Please select]
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