Nature and development of plants . dies of variousforms, called ascocarps or perithecia, are developed which oftenbecome the conspicuous part of the fungus (Figs. 143, 144).The ascospores germinate immediately or after a period of restand form a new mycelium. It should be stated that the asco-carps have not been connected, in many cases, with sexual proc-esses, and it is inferred that sexuality has been lost along withother characters as a consequence of the degeneracy resultingfrom parasitic and saprophytic habits. Only a few of the moreimportant orders will be discussed. 83. Order a. Yeast o
Nature and development of plants . dies of variousforms, called ascocarps or perithecia, are developed which oftenbecome the conspicuous part of the fungus (Figs. 143, 144).The ascospores germinate immediately or after a period of restand form a new mycelium. It should be stated that the asco-carps have not been connected, in many cases, with sexual proc-esses, and it is inferred that sexuality has been lost along withother characters as a consequence of the degeneracy resultingfrom parasitic and saprophytic habits. Only a few of the moreimportant orders will be discussed. 83. Order a. Yeast or Saccharomycetes.—These fungi areunicellular plants and many regard them as reduced do not produce a mycelium, but consist of rather oval cellswhich multiply by a budding process shown in Fig. [39, .7. B. DEVELOPMENT OF PLANTS 207 The new cells that push out from the side of the mother cellreadily drop off, but in rapid growth they may remain attachedin chains (Fig. 139, D). Under certain conditions, as the ex-. Fig. 139. The yeast plant, Saccharomyces: A, single plant. B, plantproducing three buds. C, section of two plants showing buds and nucleardivision. D, chain of plants due to rapid budding and growth. E, forma-tion of ascospores. F, germination of an ascospore and the formation ofnew plants by budding.—After Wager. haustion of the food supply, the cells become transformed intoasci and the contents of each cell rounds off into one or moreascospores (Fig. 139, E). The ascospores are freed by the decayof the ascus and when conditions are favorable, grow into thecharacteristic yeast cells, as shown in Fig. 139, F. (a) Fermentation.—These microscopic plants must be num-bered among those plants that are of the greatest economic importance is due to the fact that they decompose sugarsupon which they feed into C02 and alcohol, a change called fer-mentation. The extensive brewing and distilling industries allover the world are dependent upon th
Size: 1689px × 1480px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisher, booksubjectplants
