18 CULTURAL STUDIES OF SPECIES OF PENICILLIUM. 



Conidiophore. — The essential data as to conidiophores are their 

 length, septation, the diameter of their cells, and especially their origin 

 and relation to the substratum and to each other. Although ex- 

 tremes of variation in length of conidiophore may be very marked in 

 any culture, the majority of conidiophores in any such culture ap- 

 proximate an average length. This length to be most reliable must 

 be taken from the origin in another hypha to the lowest branch of the 

 fructification. If the conidial fructification were counted into the 

 length, the length of conidiophore would in many case's be doubled 

 with the maturing of the spores. The actual length, however, is little 

 changed with such maturity. Valid data on these points can be 

 secured in many species only by direct observation of the undis- 

 turbed colony in the air under the microscope, instead of by the study 

 of fluid mounts. This is equivalent to saying that Petri dishes, or 

 other vessels which can be uncovered for study, must be used. The 

 student must expect, therefore, to make many cultures and jeopardize 

 the purity of one such culture every time he undertakes its proper 

 examination. 



Conidial fructification. — For lack of a better term conidial fructifica- 

 tion maybe defined as including the chains of conidia, the conidiiferous 

 cells, and the branches bearing them back to their junction with the 

 conidiophore proper. In a species of Penicillium fructifications vary 

 greatly in detail, so that satisfactory illustration becomes difficult. 

 Comparison of large numbers of fruiting branches in many cultures of 

 the several species establishes specific types of appearance which can 

 be shown in a conventionalized series of sketches for each species. 

 The data found of value have been the mode of branching, the meas- 

 urements of branches and conidiiferous cells, the relation of these to 

 each other, the arrangement of the chains of conidia with reference to 

 each other, and the measurement and appearance of the fructification 

 as a whole. These penicillate fructifications vary from close columns 

 of spores arising from single verticils of cells borne directly upon the 

 apices of the conidiophores to widely spreading "brooms" whose 

 numerous divergent chains arise from verticillately or complexly 

 arranged branches from the original conidiophores. In the study of 

 these conidial fructifications mounting in fluid commonly greatly dis- 

 arranges these complex masses of branches and spore chains. Direct 

 observation of the undisturbed colony is therefore essential to a cor- 

 rect conception of the habits of the species, though the details of 

 branching and spore bearing must be sought in fluid mounts. 



The term " conidiiferous cell " is used for the cell at the base of every 

 chain of conidia in preference to "sterigma, " as often used, or to 

 "basidium" as used by Stoll. 24 The term was proposed by Professor 

 Atkinson as meeting the objection that basidium implies a relation- 

 ship net justified in fact, while sterigma usually designates not a spore- 



