Fungi, Ascomycetes, Ustilaginales, Uredinales . inishes the probability that this isa primitive type, or one that has given riseto cup-shaped forms, and it seems easier tothink of Genea and its allies as derived fromthe Pezizales by the diminution in size ofthe external aperture, the shortening andbroadening of the ascus and the increasedconvolution of the hymenium, than to regardthem as giving rise to that group by thecontrary changes. It is, however, not impro-bable that the Pezizales are polyphyletic inorigin, and that some of them may have beenderived from the higher Geoglossaceae. So far
Fungi, Ascomycetes, Ustilaginales, Uredinales . inishes the probability that this isa primitive type, or one that has given riseto cup-shaped forms, and it seems easier tothink of Genea and its allies as derived fromthe Pezizales by the diminution in size ofthe external aperture, the shortening andbroadening of the ascus and the increasedconvolution of the hymenium, than to regardthem as giving rise to that group by thecontrary changes. It is, however, not impro-bable that the Pezizales are polyphyletic inorigin, and that some of them may have beenderived from the higher Geoglossaceae. So far we have considered mainly theexternal characters of the fruit and the struc-ture of the ascus, but when we turn to thePezizales we find a further, and possibly a more valuable, criterion in thestructure of the sexual organs. The antheridium is known in very few cases. A large, oblong coenocyticcell has been described in Ascodcsmis, and a similar, though larger, i ,min Pyronema and in Lachnea stercorea, and we have also, if its position. Fig. 55. Sepultaria coron M uniseriate spores ; ascus opening bya lid; branched, septate, clavateparaphyses; x 600. 7 98 DISCOMYCETES [ch. should be ultimately established, the curious stalked conidium of Ascoboluscarbonarius. The archicarp is of much commoner occurrence, and seems more likelyto be useful as a gauge of relationship. Among Discomycetes the simplesttype is undoubtedly that of Ascodesmis or Thelcbolus; the significant detailsin Thelebohis are not fully known, but in Ascodesmis we have a stout, twistedhypha, divided into three parts, the unicellular trichogyne, the unicellularcoenocytic oogonium and the multicellular stalk (fig. 56). After fertilization
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfungi, bookyear1922
