28 A MANUAL OF THE ASPERGILLI 



The Ascospore 



So far as fully described, the ascospore of Aspergillus follows the general 

 type shown in the figures and description of DeBary. In the course of 

 its development, the secondary thickening of the cell-wall develops in 

 the form of two symmetrical valves suggesting the arrangement found 

 in the shell of a bivalve mollusk, such as the hard clam (Venus mercenaria). 

 The ripe ascospore is commonly shaped as a double convex lens with the 

 valves more or less closely in contact at the edges. A series of variations 

 upon this basic pattern occur and characterize particular species (figs. 27, 

 34, and 43). If the exospore is smooth and the margin of the valves is 

 not marked by folds or ridges, figure 27A characteristic of A. re-pens appears; 

 if the exospore is rough in the absence of marginal folds, figure 27D 

 characteristic of A . amstelodami results ; if the exospore is rough and the 

 margin of the valves bear folds or ridges, figure 43C characteristic of A. 

 rugulosus and A. jischeri is produced. An extreme development of the 

 marginal folds is seen in- A. variecolor, figure 43D. 



When such an ascospore germinates (fig. 8A), the figure first shown by 

 DeBary (1854) develops. Exactly the same type of germination is shown 

 by A. nidulans, in which as the spore swells, the valves first separate at 

 one edge, then parting completely, remain on opposite sides of the germi- 

 nated spore conspicuously identifiable by the bright purple-red color of 

 the valves (Thorn and Church, 1926). 



Htille Cells 



Mature perithecia were described for A. nidulans by Eidam (1883) 

 but without giving attention to their origin. In his description, Eidam 

 pictured a loose network of hyphae more or less completely surrounding 

 the perithecium containing large numbers of "Hiille" cells, terminal or 

 intercalary cells which swell and become vesiculose, elliptical or almost 

 globose, then develop very heavy thick walls almost obliterating the cell 

 lumen (fig. 49). These cells were later noted by Dangeard (1907) who 

 designated them as chlamydospores, but failed to present evidence of 

 function as propagative cells. These cells are abundant in connection 

 with perithecia in all strains of the A. nidulans group, but are lacking in 

 A. unguis which does not produce perithecia. Cells of the same general 

 character appear in sterile masses of hypae in strains of the A. ustus and 

 A. flavipes groups (fig. 49), and in some strains of the A. versicolor group, 

 while thick- walled, septate hyphae at least suggestive of hiille cells appear 

 in Aspergillus carneus in the A. terreus group (fig. 49F). 



In the .4 . nidulans group hiille cells, "Eidamsche blasen," or chlamydospore 

 (terms found in the literature) are always produced in connection with 

 perithecium formation (fig. 42). In the A. flavipes, A. ustus, and A. 



