. A textbook of botany for colleges and universities ... Botany. SAPROPHYTISM AND SYMBIOSIS 8oi. considerable change may have been wrought in the latter through symbi- osis. In fact, experiments have shown that lichen fungi when grown independ- ently differ in form and in chemical composition from the same fungi when grown in symbiosis with algae. While the lichen body is that of the fungal symbiont, it is generally quite unlike ordinary fungus bodies, being flat, com- pact, and expanded like a liverwort. Since the algae make up what may be called the synthetic tissue, the advantage of the fla
. A textbook of botany for colleges and universities ... Botany. SAPROPHYTISM AND SYMBIOSIS 8oi. considerable change may have been wrought in the latter through symbi- osis. In fact, experiments have shown that lichen fungi when grown independ- ently differ in form and in chemical composition from the same fungi when grown in symbiosis with algae. While the lichen body is that of the fungal symbiont, it is generally quite unlike ordinary fungus bodies, being flat, com- pact, and expanded like a liverwort. Since the algae make up what may be called the synthetic tissue, the advantage of the flat expanded surface is'as evident as in liverworts. The autonomous features of lichens. — In spite of the proven duality of lichens, there are various things which suggest that they possess a high degree of auton- omy or unity. It is quite conceivable that this autonomy might ultimately be- come so complete as to make impossible the separate cultivation of the two symbionts. Perhaps the most strik- ing evidence of autonomy is afforded by the soredia (figs. 1114-1116), which are unique reproductive or- gans consisting of a group of algal cells invested by fungal hyphae; at maturity the soredial structure buds ,,]5 j|,g off from the lichen thallus like a Figs. 1114-1116.— Soredia from the gemma (p. 808), forming, perhaps, beard lichen (JJsnca barbata): 1114, a the most efficient means of repro- simple soredium, consisting of an algal ^^^^^^^ possessed by lichens, since cell, surrounded by a web of fungal by- , , , r 1 1 phae; 1115, a soredium in which the algal the fungal spores are of value only cell has reproduced by division; iri6, a when they happen tO fall among germinating soredium in which the algae appropriate algae. This is almost are dividing, the hyphae forming an apex of growth; all Bgures highly magnified, the Only case where two symbionts — From ScHWENDENER. have a common reproductive body.' • The fungal symbiont of Lolium is scattered with the seeds, the myc
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
