612 MEDICAL MYCOLOGY 



giving the macroscopic appearance of a stalk and conidial head (Fig. 90, 2). 

 Thorn (1930) reports that coreminm formation oeonrs following the develop- 

 ment of trailing or ascending ropes of hyphae which anastomose in a char- 

 acteristic manner, or when the mycelium produces all or part of its conidio- 

 phores in clusters or fascicles with or without sterile or partially sterile areas 

 between. These fascicles, developing in a conidial area otherwise velvety, 

 give a rough or uneven appearance to the margin which has sometimes been 

 described as mealy. 



The funiculose type is characterized by aerial ropes or bundles of several 

 to many hyphae branching and interlacing over the surface, ascending, but 

 rarely if ever vertical. In these species part or all of the fertile hyphae arise 

 as branches from these ropy networks, although usually some simple conidio- 

 phores are found (Figs. 90, 5 and 91). 



For most species, correct information as to the relationship between sub- 

 merged mycelium and conidiophores can be clearly observed only at the 

 margin of the colony. Often a slowly growing colony is much easier to ob- 

 serve than a rapidly growing one. Zonation of surface growth is conspicuous 



Fig. 91. — Diagrammatic radial section of a colony of Paecilomyces Varioti showing loose 

 submerged hyphae, dense mycelial layer at the surface, aerial trailing hyphae and ropes of 

 hyphae bearing penicilli (X25). (After Thorn 1930.) 



in many species (Munk 1912). UHscheck offers the hypothesis that zonation 

 appears when colonies grow rapidly, secrete enzymes, and produce by-prod- 

 ucts of their metabolism in such concentrations that they reduce or suppress 

 growth and conidial formation in such zones. The mycelium grooving through 

 these zones into fresh nutrients resumes vigor of growth and reproduction 

 only to be depressed again by the excessive by-products of this heightened 

 activity. The extension of the colony thus gives the appearance of zonation. 

 The conidiophores which arise from the mycelium as vertical, aerial 

 hyphae, are highly differentiated. In Aspergillus a mycelial cell enlarges, 

 becomes thick-walled, and often variously contorted. From this cell, often 

 called the foot cell, a vertical branch develops, usuallj^ midway between the 

 ends. This branch, known as the stalk, usually having thick walls and thin 

 septa, enlarges upward toward the top where it dilates into a pyriform to 

 nearly spherical vesicle. In the Aspergillus glaucus group, the septa are thick 

 and the stalk is often referred to as articulate. The thickening of the stalk 

 walls may be smooth, or pitted, or warted. These characteristic markings 



