Thom: Conidium Production in Penicillium 213 
Connective 
Once formed, the conidium reaches characteristic form and size 
by swelling and laying down new walls for itself within the pri- 
mary wall which is continuous with that of the parent cell. The 
appearance of a connective (bridge, or disjunctor) is due to this 
old wall. The presence of this connective is figured by various 
authors and noted as common, but without explanation by West- 
ling. The appearance arises in certain species 4 and especially in 
particular media from the swelling and rounding up of the new 
cell within the old wall. Such formation is more frequent in 
Fig. i. Conidium formation and the connective in Penicillium : a, conidium- 
bearing cell showing the tube and a conidium in its elliptical stage ; b, d, f, 
chains of conidia showing different appearances of the connective but no cross- 
walls ; c, e, chains of conidia in which the original cross-wall shows. 
media poor in nutrients especially in carbohydrates. In such cases 
the new wall following the plasma membrane, splits away from 
the old at the ends of the cell leaving an apparently empty space 
bridged across by the lines made by the primary wall. In espec- 
ially favorable cases the original cross wall can be traced. Com- 
monly the cells remain in contact with the center of the cross-wall 
where doubtless protoplasmic connections from cell to cell are con- 
tinued for some time. In many cases, interpretation of the ap- 
pearance would be impossible unless the true arrangement of 
walls had been traced out in these favorable forms. 
* These statements are equally true for all species of Aspergillus examined 
by the writer. 
