7o 



PLECTOMYCETES 



[CH. 



the outer filaments form four or five parenchymatous layers which constitute 

 a protective sheath, apparently differing but little from that of Eurotium or 

 Penicillium. 



In the investigated species of the genus Eurotium {Aspergillus), the 

 ascospores and conidia are commonly multinucleate and give rise on ger- 

 mination to a septate mycelium each cell of which contains several nuclei. 



Conidiophores appear early; they arise as a rule from densely tangled 

 knots of swollen mycelium, and appear as thick, multinucleate hyphae. The 

 tip of the conidiophore becomes swollen and rounded off and its cytoplasm 

 shows a reticulate arrangement. A little later numerous sterigmata bud 

 out (fig. 29), and the nuclei stream up the strands of cytoplasm towards 



Fig. 29. Eurotium herbariorum (Wigg.) Link; development of conidiophores and conidia, 



x 6 2 ~ . 



them. Several nuclei pass to each sterigma and thence to the conidia which 

 develop in acropetal succession. At maturity each conidium contains in 

 E. repens about twelve nuclei, in E. herbariorum four, and in E. fumigatus, 

 E.flavus and E. clavatus, as described by Dangeard, only one. 



The general features of the sexual organs of Eurotium herbariorum were 

 described by de Bary in his classical researches of 1870. He distinguished 

 a coiled, septate archicarp, and saw that its tip fused with a comparatively 

 straight antheridial hypha, the membranes between breaking down, and he 

 recognized that from it the asci are ultimately derived. 



More recently it has been shown that the archicarp of Eurotium is 

 made up of three parts: a multicellular stalk, a unicellular oogonium, and 

 a unicellular trichogyne. In E. herbariorum these parts may be clearly 

 distinguished (fig. 30^), but they are not always equally definite in E. repens. 



