. Outlines of botany for the high school laboratory and classroom (based on Gray's Lessons in botany) Prepared at the request of the Botanical Dept. of Harvard University. Botany; Botany. CRYPrOGAMS 197 we come to the real Mosses. A section tlu'ougli a Lichen thallus (Fig. 331) sliows hirge numbers of green cells having much the appearance of such unicellular Algie as Pleurococcus and Nostoc, held in the meshes of a tissue made up of hlaraeiits resembling Fungus hypha'. These appearances represent the truth (jf the matter. Ijichons arc composite growtlis in which certain uniccUidar AlgiE and c
. Outlines of botany for the high school laboratory and classroom (based on Gray's Lessons in botany) Prepared at the request of the Botanical Dept. of Harvard University. Botany; Botany. CRYPrOGAMS 197 we come to the real Mosses. A section tlu'ougli a Lichen thallus (Fig. 331) sliows hirge numbers of green cells having much the appearance of such unicellular Algie as Pleurococcus and Nostoc, held in the meshes of a tissue made up of hlaraeiits resembling Fungus hypha'. These appearances represent the truth (jf the matter. Ijichons arc composite growtlis in which certain uniccUidar AlgiE and certain Fungi take jtart. Figure 332 shows how tliis union l>e- gins. The spore of a Fiuigus has fallen near a cell of Pleurococcus. The young mycelium is already ap- plied to the Alga, whicli has divided. Further development consists in the extension. 3:!l. Section ol' a liclieu tliiinus. A B 332. First stages in tlio I'omiatiiin of the lichen thallus. — BOBNET. and lii'iindiing of the mycelium, and (lie midti- jilicatiou of the algal cells; the construction, l)y these means, of a tliallus having certain distinguishing peculiarities of structure, according to the kind of Fungus and the kind of iMga concerned ; and finally, the prodtietion of a spure-ljearing l)ody. In many Lichens this fructification is an apo- thecium (Fig. 3211, «) very like that of Peziza, with a hymenium con- taining spore sacs or asci (Fig. 333). Most of the Lichen Fungi are Sac Fungi. They are parasitic upon the Algte and cannot exist without tliem. The Alg;e, however, are known to be able to exist perfectly well without the Fungi.^ 333. Section of an apfiilie- ciuni. 1 Symbiosis (as the word is understood among English-speaking botanists) is the living together of unlike organisms for jnutiial advan- tage. Many botanists regard Lichens as examples of symbiotic acouni- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabilit
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