STUDY OF PENICILLIUM IN KETCHUP. 29 



DEVELOPMENT. 



In developing, the mold forms a white felt-like mass, covering the 

 medium on which it is growing; then as development proceeds, it 

 changes to bluish-green, and finally to a darker, duller color. The 

 change in color is accompanied by a change in structure, the surface 

 becoming powdery in appearance, a slight current of air being suffi- 

 cient to dislodge a cloud of fine dust. This fine dust is formed of 

 small, spherical bodies, the spores or conidia (from the Greek meaning 

 dust) . These need no resting period, but are able to develop at once. 

 When the conidia lodge on a moist substance they swell to a much 

 greater size and then send out a tube from some part of their surface. 

 The tube lengthens and septa form, dividing the tube into sections, 

 or cells. At the same time branches are sent out, which again form 

 other branches. The original conidium sends out a second branch 

 shortly after the first one, and usually from the opposite side, and 

 may even send out a third one. The formation of the septa and the 

 subbranching goes on in all, so that in a short time the branches mat 

 together and form a felt-like cover. 



REPRODUCTION. 



After a shorter or longer period of development, dependent on the 

 conditions, branches are sent perpendicularly from the substratum, 

 and into the air. These branches cease their growth in length, sending 

 out branches near the tip, which take the same general direction as 

 the original branch. Each of these subbranches is called a sterigma 

 (from the Greek word meaning support). In vigorous development 

 the sterigmata may form secondary branches, the whole forming a 

 tassel-like arrangement. The tip of a sterigma enlarges, a septum 

 forms around the enlargement, cutting it off from the sterigma, and 

 forming a conidium. The sterigma develops to the original length 

 and another conidium is formed, the operation being repeated many 

 times, thus forming a chain of spores. As the other sterigmata are 

 also forming conidia in the same manner, a series of these chains is 

 formed close together. After the cessation of conidial development, 

 the filament below the sterigmata is disorganized, setting free the 

 conidia. The filament and head together are called the conidiophore 

 (Greek, dust-bearer). 



Penicillium forms spores sexually, but the conditions for their for- 

 mation are unknown. Brefeld obtained them by growing the mold 

 on damp bread placed between two glass plates, and excluding the 

 air. Lindner obtained carpospores on a wort gelatin culture in a 

 petri dish, from which the air was excluded. The writer has tried 

 various methods for obtaining carpospores, but so far without success. 

 Moist chambers were used with various media, excluding the air. 



