. Botany of the living plant. Botany. (/;) ZYGOMYCETES because there is no recognisable dilloreiue of form or stnirtiin*. hut onlv of function. If cither l)e cultivated puro, and ai)art, tlw liean* no zygospores. But if cultures of the + and - types l>c rt ami meet, a profuse formation of zygosjiores appears along the lun- ..i (Fig. 361). The behaviour is thus similar to that seen in tmi'^rx-!.,! ]A^n\% Functionally the Homothallic may be compared with the Maw the Heterothallic with the Dioecious state. J^ut these (â st not be pressed too closely. The facts thus dis
. Botany of the living plant. Botany. (/;) ZYGOMYCETES because there is no recognisable dilloreiue of form or stnirtiin*. hut onlv of function. If cither l)e cultivated puro, and ai)art, tlw liean* no zygospores. But if cultures of the + and - types l>c rt ami meet, a profuse formation of zygosjiores appears along the lun- ..i (Fig. 361). The behaviour is thus similar to that seen in tmi'^rx-!.,! ]A^n\% Functionally the Homothallic may be compared with the Maw the Heterothallic with the Dioecious state. J^ut these (â st not be pressed too closely. The facts thus disclosed give a ready expUination of the rarity of zygospores in certain cases, and their frequency in others. The facts of the life-history in the Zygomycetes show a less direct dependence of these plants on external fluid water than in the Oomy- cetes, for there are no zoospores motile by cilia. Still the dissemina- tion of the spores in the Mucors is through swelling of mucilage in water, or ejection where fluid pressure gives the propulsive Fig. 361. Result of a plate-culture of the heterothallic Mucor htcmaUs, made by .Mr. Drumraond. + and â strains were started on opposite sides of the plate. The dark line transversely between these shows where the cultures meet, and the lyjco- spores were formed, {h natural size.) The series with branched sporangiophores, and wind-borne conidia is a step still further away from dependence upon the water-medium. Comparison suggests for the more primitive sporangia siich as Mucor an origin from a sporangium like that of a Siphonaceous Alga. The loss of motility of the spores which is involved is readily under- stood in organisms living in moist air in place of water. The formation of zygospores presents the unusual condition of the fusion not of single cells as in the Conjugatae, but of coono- gametes to form a coeno-zygote. There is reason to believe that numerous nuclear fusions take place ⢠in fact that the formation of the z
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
