Thom: Conidium Production in Penicillium 215 
formed in primary, secondary or tertiary branching groups or 
verticils in the same fruit mass. In other species it would be 
necessary to record metulae as absent so that the conidia-bearing 
verticils would be produced directly upon the apices of the conidio- 
phore and its branches. This latter conception can be readily 
applied in a few species. Descriptions and figuring of branching 
systems as typical for species involves many difficulties as is 
recently noted by Wehmer . 5 In the same culture, corresponding 
septa of different conidial masses may show, single, opposite, or 
verticillate branching, with a change of nutrient the variation may 
be carried in one direction or another. Literal following of the 
keys furnished for generic discrimination might place different 
fruits of the same colony in several genera. 
United States Department of Agriculture, 
Washington, D. C. 
s Wehmer, C. Mycologisches Centralblatt, Bd. II (1913), heft 4, p. 197. 
