A text-book of mycology and plant pathology . plied to the parasite. Such spores are bornein a sorus known as a telium. When these teliospores germinate, theyproduce a four-celled promycelium known as a basidium, and thisabstricts sporidia, or more properly basidiospores, which are minute,thin-walled spores without surface sculpturings. These are succeededby spermogonia (spermogonium), which are now called by most 187 I88 MYCOLOGY American mycologists, pycnia (pycnium), in which spermatia, orpycniospores, are formed. Pycnia indicate the nature of the life cycleand furnish positive characters f
A text-book of mycology and plant pathology . plied to the parasite. Such spores are bornein a sorus known as a telium. When these teliospores germinate, theyproduce a four-celled promycelium known as a basidium, and thisabstricts sporidia, or more properly basidiospores, which are minute,thin-walled spores without surface sculpturings. These are succeededby spermogonia (spermogonium), which are now called by most 187 I88 MYCOLOGY American mycologists, pycnia (pycnium), in which spermatia, orpycniospores, are formed. Pycnia indicate the nature of the life cycleand furnish positive characters for identification. Arthur has shownthat if pycnia and urediniospores are found arising from the samemycelium, aecidia do not occur in the cycle; and if pycnia and telio-spores are found there are neither uredinia nor secia in the life pycnospores are accompanied or succeeded by aeciospores(aecidiospores), which appear in the cluster cups, or aecia in long peridia of the different kinds of aecia are variable, and hence. Fig. 64.—Spore forms of wheat rust, Pucainia graminis. A, Section throughbarberry leaf showing pycnia on upper surface and Eecia on lower; B, two uredinio-spores; C, germinating urediniospore; D, teliosorus showing several teliospores; E,single two-celled teliospore; F, germinating teliospore with four-celled basidium andtwo basidiospores; C, basidiospore growing on barberry leaf. (Adapted from deBary.) mycologists have described four different kinds of form genera: CcBoma= peridium absent; jEcidimn = cup-shaped and peridium toothed;Rcestelia = peridium elongate and fimbriate; Peridermium = peri-dium irregularly split and broken. Urediniospores (uredospores)succeed the aeciospores and they appear in sori known as uredinia(uredinium). Amphispores are special forms of urediniospores formedin arid, or semi-arid climates and usually have a thick cell wall and apersistent pedicel. They are in the nature of a resting spore. Meso-spores are exa
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