. Essentials of biology presented in problems. Biology. 150 THE VARIOUS FORMS OF PLANTS spores have been formed by the division of the protoplasm mak- ing up the ball or sporangium into many separate bodies. This method of the production of spores is evidently asexual. These spores, if grown imder favorable conditions, will produce more mycelia, which in turn bear sporangia. It has been found, however, that at some time during the life of the mold another method of reproduction is likely to occur. Formation of Zygospores. — Two hyphse which are close-lying put out threads which communicate. Th
. Essentials of biology presented in problems. Biology. 150 THE VARIOUS FORMS OF PLANTS spores have been formed by the division of the protoplasm mak- ing up the ball or sporangium into many separate bodies. This method of the production of spores is evidently asexual. These spores, if grown imder favorable conditions, will produce more mycelia, which in turn bear sporangia. It has been found, however, that at some time during the life of the mold another method of reproduction is likely to occur. Formation of Zygospores. — Two hyphse which are close-lying put out threads which communicate. The end of each of the threads cuts off a cell, and the two cells, each from a different hypha, flow together and mingle. In this condi- tion they remain as a single resting cell. This cell, which puts a heavy ID wall around itself, is a zygospore. Here again we have a process of con- jugation similar to that we observed in the pond scum. The ultimate re- sult of the conjugation of the two cells is that a new plant grows from the zygospore after a period of rest. Dur- ing the resting stage the spore may undergo very unfavorable conditions, even to extreme dryness, heat, or cold. Conjugation of black mold: A, The use of the Zygospore to the plant B, C, D, successive stages in jg evidently to Continue the species the formation of the zygospore, ^^^j^^ ^^ unfavorable time in the life history of the plant. The process of conjugation is probably a sexual process, as we have called it in pond scum. Physiology of the Growth of Mold. — Mold, in order to grow rapidly, evidently needs oxygen, moisture, and heat. It obtains its food from the material on which it lives. This it is able to do by means of digestive ferments which are given out by the rhizoids or rootlike parts of the hyphae, by means of which the mold clings to the bread. These ferments change the starch of ' It seems to have been proved recently that zygospores are formed by the union of two cells, from different filament
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