Science . may come from the samebranch, even if they are in some species ofdifferent size. In dioecious species zygo-spores have been obtained from matings ofmale and female races which in one speciescame from as diverse regions as China andCambridge, Mass. In such forms the en-vironmental conditions under which thesexually opposite races have grown may besufficiently different to furnish a basis forthe advantages assumed to accrue from ablending of maternal and paternal char-acters in the offspring. The mueors form the only group of thelower cryptogams in which the presence ofsexual races has
Science . may come from the samebranch, even if they are in some species ofdifferent size. In dioecious species zygo-spores have been obtained from matings ofmale and female races which in one speciescame from as diverse regions as China andCambridge, Mass. In such forms the en-vironmental conditions under which thesexually opposite races have grown may besufficiently different to furnish a basis forthe advantages assumed to accrue from ablending of maternal and paternal char-acters in the offspring. The mueors form the only group of thelower cryptogams in which the presence ofsexual races has been demonstrated. In plants a differentiation is more or lessapparent into a stage bearing the gametesand a stage bearing the spores. The accom-panying figures represent diagrammatic-ally the sexual character of these two stagesin certain groups of plants. The stage Mabch 8, 1907] SCIENCE 369 s w §. XH 0+ -PO WW w W W / ^^ t/2 H 1—1 CMO « pq W <^ ^ 1—( 1—1 1—1 fi r^ o o w n o p ^ WW w Of WWWscience251907mich. 388
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