The elements of botany for The elements of botany for beginners and for schools elementsofbotany00gray Year: 1887 SECTION 17.] 171 set free is ready to germinate. Fig. 565 represents several stapes of the Conjugating process, which, however, would never he found all together like this in one pair of threads. 513. Desinids and Diatomes, which are microscopic one-celled plants of the same class, conjugate in the same way. as is shown in a Closterium by Fig. 566, 567- Here the whole living contents of two individuals are in- corporated into one spore, for a fresh start. A reprod
The elements of botany for The elements of botany for beginners and for schools elementsofbotany00gray Year: 1887 SECTION 17.] 171 set free is ready to germinate. Fig. 565 represents several stapes of the Conjugating process, which, however, would never he found all together like this in one pair of threads. 513. Desinids and Diatomes, which are microscopic one-celled plants of the same class, conjugate in the same way. as is shown in a Closterium by Fig. 566, 567- Here the whole living contents of two individuals are in- corporated into one spore, for a fresh start. A reproduction which costs the life of two individuals to make a single new inn- would be fatal to the species if there were not a provision for multiplication by the prompt divi- sion of the new-formed individual into two, and these again into two, and so on in geometrical ratio. And the costly process would be meaningless if there were not some real advantage in such a fresh start, that is, in sexes. 514. There arc other Alga? of the grass-green series which consist of single cells, but which by continued growth form plants of considerable size. Three kinds of these are represented in Fig. 568-574. 515. Lichens, Latin Lichenes, are to be studied in the works of the late Professor Tnckerman, hut a popular exposition is greatly needed. The subjoined illustrations (Fig. 575-580) may simply indicate what some of the commoner forms are like. The cup, or shield-shaped spot, or knob, which bears the fructification is named the Apothecium. This is mainly 568. Early sta^c of a species of Hotrydium, a globose cell. 669, 570 of growth. 571. Pull-grown plant, extended and ramified below in i root-like way. :'>7'J A Vaucheria; single cell grown on Into a much-branched thread; the eml of some brandies enlarging, and the green contents In one (a) there condensed into :i spore. 573. More magnified riew f <i, and the mature spore escaping. 574. Bryopsis plumosa; apex of a stem with Its
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