FIG 1.

Analysis of perithecial development in N. crassa. (A to F) Sections of perithecia demonstrate the expansion of the perithecium wall (PW), composed of thick-walled cells, and the development of thin-walled cells in the centrum parenchyma (CP), except as noted. (G to L) Light microscopic analysis of perithecial squashes show internal contents of the fruiting body, including centrum parenchyma, asci (AS), and ascospores. (A) By 24 h, the perithecia show an initial expansion of the centrum parenchyma, which is surrounded by multiple layers of thick-walled cells composing the perithecium wall. Magnification, ×400. (B) At 48 h, early paraphyses (PP) appear as elongated cells within the expanded centrum parenchyma (×200). The initial ostiole (OS) forms at the apex of the fruiting body. (C) At 72 h, abundant paraphyses arise from thin-walled cells at the bottom of the centrum. The ostiole has formed and is lined with periphyses, and layers of the perithecial wall are distinct (×200). (D) At 96 h, early asci are beginning to appear (×200). (E) At 120 h, early ascospores start developing in some asci (×200). (F) At 144 h, melanized ascospores are visible in many asci. The beak and ostiole appear fully developed at the apex of the fruiting body (×200). (G) By 24 h, the perithecium has grown, but a squash does not reveal differentiation of hyphae within the perithecium (×200). (H) At 48 h, thin-walled cells of the centrum parenchyma have clearly differentiated (×400). (I) At 72 h, early paraphyses appear (×400). (J) At 96 h, early asci extend from thin-walled cells at the base of the centrum (×400). (K) At 120 h, ascospores begin to form in asci (×400). (L) At 144 h, eight ascospores can be distinguished in a well-developed ascus (×400).